diff options
Diffstat (limited to 'Documentation/howto')
| -rw-r--r-- | Documentation/howto/keep-canonical-history-correct.txt | 216 | ||||
| -rw-r--r-- | Documentation/howto/maintain-git.txt | 376 | ||||
| -rw-r--r-- | Documentation/howto/new-command.txt | 104 | ||||
| -rw-r--r-- | Documentation/howto/rebase-from-internal-branch.txt | 19 | ||||
| -rw-r--r-- | Documentation/howto/rebuild-from-update-hook.txt | 12 | ||||
| -rw-r--r-- | Documentation/howto/recover-corrupted-blob-object.txt | 20 | ||||
| -rw-r--r-- | Documentation/howto/recover-corrupted-object-harder.txt | 479 | ||||
| -rw-r--r-- | Documentation/howto/revert-a-faulty-merge.txt | 108 | ||||
| -rw-r--r-- | Documentation/howto/revert-branch-rebase.txt | 22 | ||||
| -rw-r--r-- | Documentation/howto/separating-topic-branches.txt | 4 | ||||
| -rw-r--r-- | Documentation/howto/setup-git-server-over-http.txt | 30 | ||||
| -rw-r--r-- | Documentation/howto/update-hook-example.txt | 52 | ||||
| -rw-r--r-- | Documentation/howto/use-git-daemon.txt | 5 | ||||
| -rw-r--r-- | Documentation/howto/using-merge-subtree.txt | 4 | ||||
| -rw-r--r-- | Documentation/howto/using-signed-tag-in-pull-request.txt | 217 |
15 files changed, 1487 insertions, 181 deletions
diff --git a/Documentation/howto/keep-canonical-history-correct.txt b/Documentation/howto/keep-canonical-history-correct.txt new file mode 100644 index 0000000000..35d48ef714 --- /dev/null +++ b/Documentation/howto/keep-canonical-history-correct.txt @@ -0,0 +1,216 @@ +From: Junio C Hamano <gitster@pobox.com> +Date: Wed, 07 May 2014 13:15:39 -0700 +Subject: Beginner question on "Pull is mostly evil" +Abstract: This how-to explains a method for keeping a + project's history correct when using git pull. +Content-type: text/asciidoc + +Keep authoritative canonical history correct with git pull +========================================================== + +Sometimes a new project integrator will end up with project history +that appears to be "backwards" from what other project developers +expect. This howto presents a suggested integration workflow for +maintaining a central repository. + +Suppose that that central repository has this history: + +------------ + ---o---o---A +------------ + +which ends at commit `A` (time flows from left to right and each node +in the graph is a commit, lines between them indicating parent-child +relationship). + +Then you clone it and work on your own commits, which leads you to +have this history in *your* repository: + +------------ + ---o---o---A---B---C +------------ + +Imagine your coworker did the same and built on top of `A` in *his* +repository in the meantime, and then pushed it to the +central repository: + +------------ + ---o---o---A---X---Y---Z +------------ + +Now, if you `git push` at this point, because your history that leads +to `C` lacks `X`, `Y` and `Z`, it will fail. You need to somehow make +the tip of your history a descendant of `Z`. + +One suggested way to solve the problem is "fetch and then merge", aka +`git pull`. When you fetch, your repository will have a history like +this: + +------------ + ---o---o---A---B---C + \ + X---Y---Z +------------ + +Once you run merge after that, while still on *your* branch, i.e. `C`, +you will create a merge `M` and make the history look like this: + +------------ + ---o---o---A---B---C---M + \ / + X---Y---Z +------------ + +`M` is a descendant of `Z`, so you can push to update the central +repository. Such a merge `M` does not lose any commit in both +histories, so in that sense it may not be wrong, but when people want +to talk about "the authoritative canonical history that is shared +among the project participants", i.e. "the trunk", they often view +it as "commits you see by following the first-parent chain", and use +this command to view it: + +------------ + $ git log --first-parent +------------ + +For all other people who observed the central repository after your +coworker pushed `Z` but before you pushed `M`, the commit on the trunk +used to be `o-o-A-X-Y-Z`. But because you made `M` while you were on +`C`, `M`'s first parent is `C`, so by pushing `M` to advance the +central repository, you made `X-Y-Z` a side branch, not on the trunk. + +You would rather want to have a history of this shape: + +------------ + ---o---o---A---X---Y---Z---M' + \ / + B-----------C +------------ + +so that in the first-parent chain, it is clear that the project first +did `X` and then `Y` and then `Z` and merged a change that consists of +two commits `B` and `C` that achieves a single goal. You may have +worked on fixing the bug #12345 with these two patches, and the merge +`M'` with swapped parents can say in its log message "Merge +fix-bug-12345". Having a way to tell `git pull` to create a merge +but record the parents in reverse order may be a way to do so. + +Note that I said "achieves a single goal" above, because this is +important. "Swapping the merge order" only covers a special case +where the project does not care too much about having unrelated +things done on a single merge but cares a lot about first-parent +chain. + +There are multiple schools of thought about the "trunk" management. + + 1. Some projects want to keep a completely linear history without any + merges. Obviously, swapping the merge order would not match their + taste. You would need to flatten your history on top of the + updated upstream to result in a history of this shape instead: ++ +------------ + ---o---o---A---X---Y---Z---B---C +------------ ++ +with `git pull --rebase` or something. + + 2. Some projects tolerate merges in their history, but do not worry + too much about the first-parent order, and allow fast-forward + merges. To them, swapping the merge order does not hurt, but + it is unnecessary. + + 3. Some projects want each commit on the "trunk" to do one single + thing. The output of `git log --first-parent` in such a project + would show either a merge of a side branch that completes a single + theme, or a single commit that completes a single theme by itself. + If your two commits `B` and `C` (or they may even be two groups of + commits) were solving two independent issues, then the merge `M'` + we made in the earlier example by swapping the merge order is + still not up to the project standard. It merges two unrelated + efforts `B` and `C` at the same time. + +For projects in the last category (Git itself is one of them), +individual developers would want to prepare a history more like +this: + +------------ + C0--C1--C2 topic-c + / + ---o---o---A master + \ + B0--B1--B2 topic-b +------------ + +That is, keeping separate topics on separate branches, perhaps like +so: + +------------ + $ git clone $URL work && cd work + $ git checkout -b topic-b master + $ ... work to create B0, B1 and B2 to complete one theme + $ git checkout -b topic-c master + $ ... same for the theme of topic-c +------------ + +And then + +------------ + $ git checkout master + $ git pull --ff-only +------------ + +would grab `X`, `Y` and `Z` from the upstream and advance your master +branch: + +------------ + C0--C1--C2 topic-c + / + ---o---o---A---X---Y---Z master + \ + B0--B1--B2 topic-b +------------ + +And then you would merge these two branches separately: + +------------ + $ git merge topic-b + $ git merge topic-c +------------ + +to result in + +------------ + C0--C1---------C2 + / \ + ---o---o---A---X---Y---Z---M---N + \ / + B0--B1-----B2 +------------ + +and push it back to the central repository. + +It is very much possible that while you are merging topic-b and +topic-c, somebody again advanced the history in the central repository +to put `W` on top of `Z`, and make your `git push` fail. + +In such a case, you would rewind to discard `M` and `N`, update the +tip of your 'master' again and redo the two merges: + +------------ + $ git reset --hard origin/master + $ git pull --ff-only + $ git merge topic-b + $ git merge topic-c +------------ + +The procedure will result in a history that looks like this: + +------------ + C0--C1--------------C2 + / \ + ---o---o---A---X---Y---Z---W---M'--N' + \ / + B0--B1---------B2 +------------ + +See also http://git-blame.blogspot.com/2013/09/fun-with-first-parent-history.html diff --git a/Documentation/howto/maintain-git.txt b/Documentation/howto/maintain-git.txt index 4357e26913..ca4378740c 100644 --- a/Documentation/howto/maintain-git.txt +++ b/Documentation/howto/maintain-git.txt @@ -1,53 +1,64 @@ From: Junio C Hamano <gitster@pobox.com> Date: Wed, 21 Nov 2007 16:32:55 -0800 Subject: Addendum to "MaintNotes" -Abstract: Imagine that git development is racing along as usual, when our friendly +Abstract: Imagine that Git development is racing along as usual, when our friendly neighborhood maintainer is struck down by a wayward bus. Out of the hordes of suckers (loyal developers), you have been tricked (chosen) to step up as the new maintainer. This howto will show you "how to" do it. +Content-type: text/asciidoc -The maintainer's git time is spent on three activities. +How to maintain Git +=================== - - Communication (60%) +Activities +---------- + +The maintainer's Git time is spent on three activities. + + - Communication (45%) Mailing list discussions on general design, fielding user questions, diagnosing bug reports; reviewing, commenting on, suggesting alternatives to, and rejecting patches. - - Integration (30%) + - Integration (50%) Applying new patches from the contributors while spotting and correcting minor mistakes, shuffling the integration and testing branches, pushing the results out, cutting the releases, and making announcements. - - Own development (10%) + - Own development (5%) Scratching my own itch and sending proposed patch series out. +The Policy +---------- + The policy on Integration is informally mentioned in "A Note from the maintainer" message, which is periodically posted to this mailing list after each feature release is made. -The policy. - - - Feature releases are numbered as vX.Y.Z and are meant to + - Feature releases are numbered as vX.Y.0 and are meant to contain bugfixes and enhancements in any area, including functionality, performance and usability, without regression. - - Maintenance releases are numbered as vX.Y.Z.W and are meant - to contain only bugfixes for the corresponding vX.Y.Z feature - release and earlier maintenance releases vX.Y.Z.V (V < W). + - One release cycle for a feature release is expected to last for + eight to ten weeks. + + - Maintenance releases are numbered as vX.Y.Z and are meant + to contain only bugfixes for the corresponding vX.Y.0 feature + release and earlier maintenance releases vX.Y.W (W < Z). - 'master' branch is used to prepare for the next feature release. In other words, at some point, the tip of 'master' - branch is tagged with vX.Y.Z. + branch is tagged with vX.Y.0. - 'maint' branch is used to prepare for the next maintenance - release. After the feature release vX.Y.Z is made, the tip + release. After the feature release vX.Y.0 is made, the tip of 'maint' branch is set to that release, and bugfixes will accumulate on the branch, and at some point, the tip of the - branch is tagged with vX.Y.Z.1, vX.Y.Z.2, and so on. + branch is tagged with vX.Y.1, vX.Y.2, and so on. - 'next' branch is used to publish changes (both enhancements and fixes) that (1) have worthwhile goal, (2) are in a fairly @@ -58,12 +69,15 @@ The policy. - 'pu' branch is used to publish other proposed changes that do not yet pass the criteria set for 'next'. - - The tips of 'master', 'maint' and 'next' branches will always - fast forward, to allow people to build their own - customization on top of them. + - The tips of 'master' and 'maint' branches will not be rewound to + allow people to build their own customization on top of them. + Early in a new development cycle, 'next' is rewound to the tip of + 'master' once, but otherwise it will not be rewound until the end + of the cycle. - - Usually 'master' contains all of 'maint', 'next' contains all - of 'master' and 'pu' contains all of 'next'. + - Usually 'master' contains all of 'maint' and 'next' contains all + of 'master'. 'pu' contains all the topics merged to 'next', but + is rebuilt directly on 'master'. - The tip of 'master' is meant to be more stable than any tagged releases, and the users are encouraged to follow it. @@ -72,15 +86,27 @@ The policy. users are encouraged to test it so that regressions and bugs are found before new topics are merged to 'master'. +Note that before v1.9.0 release, the version numbers used to be +structured slightly differently. vX.Y.Z were feature releases while +vX.Y.Z.W were maintenance releases for vX.Y.Z. + -A typical git day for the maintainer implements the above policy +A Typical Git Day +----------------- + +A typical Git day for the maintainer implements the above policy by doing the following: - - Scan mailing list and #git channel log. Respond with review - comments, suggestions etc. Kibitz. Collect potentially - usable patches from the mailing list. Patches about a single - topic go to one mailbox (I read my mail in Gnus, and type - \C-o to save/append messages in files in mbox format). + - Scan mailing list. Respond with review comments, suggestions + etc. Kibitz. Collect potentially usable patches from the + mailing list. Patches about a single topic go to one mailbox (I + read my mail in Gnus, and type \C-o to save/append messages in + files in mbox format). + + - Write his own patches to address issues raised on the list but + nobody has stepped up solving. Send it out just like other + contributors do, and pick them up just like patches from other + contributors (see above). - Review the patches in the saved mailboxes. Edit proposed log message for typofixes and clarifications, and add Acks @@ -96,40 +122,32 @@ by doing the following: - Obviously correct fixes that pertain to the tip of 'master' are directly applied to 'master'. + - Other topics are not handled in this step. + This step is done with "git am". $ git checkout master ;# or "git checkout maint" - $ git am -3 -s mailbox + $ git am -sc3 mailbox $ make test - - Merge downwards (maint->master): - - $ git checkout master - $ git merge maint - $ make test + In practice, almost no patch directly goes to 'master' or + 'maint'. - Review the last issue of "What's cooking" message, review the - topics scheduled for merging upwards (topic->master and - topic->maint), and merge. + topics ready for merging (topic->master and topic->maint). Use + "Meta/cook -w" script (where Meta/ contains a checkout of the + 'todo' branch) to aid this step. + + And perform the merge. Use "Meta/Reintegrate -e" script (see + later) to aid this step. + + $ Meta/cook -w last-issue-of-whats-cooking.mbox $ git checkout master ;# or "git checkout maint" - $ git merge ai/topic ;# or "git merge ai/maint-topic" + $ echo ai/topic | Meta/Reintegrate -e ;# "git merge ai/topic" $ git log -p ORIG_HEAD.. ;# final review $ git diff ORIG_HEAD.. ;# final review $ make test ;# final review - $ git branch -d ai/topic ;# or "git branch -d ai/maint-topic" - - - Merge downwards (maint->master) if needed: - - $ git checkout master - $ git merge maint - $ make test - - - Merge downwards (master->next) if needed: - - $ git checkout next - $ git merge master - $ make test - Handle the remaining patches: @@ -138,9 +156,9 @@ by doing the following: and not in 'master') is applied to a new topic branch that is forked from the tip of 'master'. This includes both enhancements and unobvious fixes to 'master'. A topic - branch is named as ai/topic where "ai" is typically - author's initial and "topic" is a descriptive name of the - topic (in other words, "what's the series is about"). + branch is named as ai/topic where "ai" is two-letter string + named after author's initial and "topic" is a descriptive name + of the topic (in other words, "what's the series is about"). - An unobvious fix meant for 'maint' is applied to a new topic branch that is forked from the tip of 'maint'. The @@ -158,7 +176,8 @@ by doing the following: The above except the "replacement" are all done with: - $ git am -3 -s mailbox + $ git checkout ai/topic ;# or "git checkout -b ai/topic master" + $ git am -sc3 mailbox while patch replacement is often done by: @@ -166,94 +185,170 @@ by doing the following: then replace some parts with the new patch, and reapplying: + $ git checkout ai/topic $ git reset --hard ai/topic~$n - $ git am -3 -s 000*.txt + $ git am -sc3 -s 000*.txt The full test suite is always run for 'maint' and 'master' after patch application; for topic branches the tests are run as time permits. - - Update "What's cooking" message to review the updates to - existing topics, newly added topics and graduated topics. - - This step is helped with Meta/UWC script (where Meta/ contains - a checkout of the 'todo' branch). + - Merge maint to master as needed: - - Merge topics to 'next'. For each branch whose tip is not - merged to 'next', one of three things can happen: + $ git checkout master + $ git merge maint + $ make test - - The commits are all next-worthy; merge the topic to next: + - Merge master to next as needed: $ git checkout next - $ git merge ai/topic ;# or "git merge ai/maint-topic" + $ git merge master $ make test + - Review the last issue of "What's cooking" again and see if topics + that are ready to be merged to 'next' are still in good shape + (e.g. has there any new issue identified on the list with the + series?) + + - Prepare 'jch' branch, which is used to represent somewhere + between 'master' and 'pu' and often is slightly ahead of 'next'. + + $ Meta/Reintegrate master..pu >Meta/redo-jch.sh + + The result is a script that lists topics to be merged in order to + rebuild 'pu' as the input to Meta/Reintegrate script. Remove + later topics that should not be in 'jch' yet. Add a line that + consists of '### match next' before the name of the first topic + in the output that should be in 'jch' but not in 'next' yet. + + - Now we are ready to start merging topics to 'next'. For each + branch whose tip is not merged to 'next', one of three things can + happen: + + - The commits are all next-worthy; merge the topic to next; - The new parts are of mixed quality, but earlier ones are - next-worthy; merge the early parts to next: + next-worthy; merge the early parts to next; + - Nothing is next-worthy; do not do anything. + + This step is aided with Meta/redo-jch.sh script created earlier. + If a topic that was already in 'next' gained a patch, the script + would list it as "ai/topic~1". To include the new patch to the + updated 'next', drop the "~1" part; to keep it excluded, do not + touch the line. If a topic that was not in 'next' should be + merged to 'next', add it at the end of the list. Then: + + $ git checkout -B jch master + $ Meta/redo-jch.sh -c1 + + to rebuild the 'jch' branch from scratch. "-c1" tells the script + to stop merging at the first line that begins with '###' + (i.e. the "### match next" line you added earlier). + + At this point, build-test the result. It may reveal semantic + conflicts (e.g. a topic renamed a variable, another added a new + reference to the variable under its old name), in which case + prepare an appropriate merge-fix first (see appendix), and + rebuild the 'jch' branch from scratch, starting at the tip of + 'master'. + + Then do the same to 'next' $ git checkout next - $ git merge ai/topic~2 ;# the tip two are dubious - $ make test + $ sh Meta/redo-jch.sh -c1 -e - - Nothing is next-worthy; do not do anything. + The "-e" option allows the merge message that comes from the + history of the topic and the comments in the "What's cooking" to + be edited. The resulting tree should match 'jch' as the same set + of topics are merged on 'master'; otherwise there is a mismerge. + Investigate why and do not proceed until the mismerge is found + and rectified. - - Rebase topics that do not have any commit in next yet. This - step is optional but sometimes is worth doing when an old - series that is not in next can take advantage of low-level - framework change that is merged to 'master' already. + $ git diff jch next - $ git rebase master ai/topic + When all is well, clean up the redo-jch.sh script with - This step is helped with Meta/git-topic.perl script to - identify which topic is rebaseable. There also is a - pre-rebase hook to make sure that topics that are already in - 'next' are not rebased beyond the merged commit. + $ sh Meta/redo-jch.sh -u - - Rebuild "pu" to merge the tips of topics not in 'next'. + This removes topics listed in the script that have already been + merged to 'master'. This may lose '### match next' marker; + add it again to the appropriate place when it happens. - $ git checkout pu - $ git reset --hard next - $ git merge ai/topic ;# repeat for all remaining topics - $ make test + - Rebuild 'pu'. - This step is helped with Meta/PU script + $ Meta/Reintegrate master..pu >Meta/redo-pu.sh - - Push four integration branches to a private repository at - k.org and run "make test" on all of them. + Edit the result by adding new topics that are not still in 'pu' + in the script. Then - - Push four integration branches to /pub/scm/git/git.git at - k.org. This triggers its post-update hook which: + $ git checkout -B pu jch + $ sh Meta/redo-pu.sh - (1) runs "git pull" in $HOME/git-doc/ repository to pull - 'master' just pushed out; + When all is well, clean up the redo-pu.sh script with - (2) runs "make doc" in $HOME/git-doc/, install the generated - documentation in staging areas, which are separate - repositories that have html and man branches checked - out. + $ sh Meta/redo-pu.sh -u - (3) runs "git commit" in the staging areas, and run "git - push" back to /pub/scm/git/git.git/ to update the html - and man branches. + Double check by running - (4) installs generated documentation to /pub/software/scm/git/docs/ - to be viewed from http://www.kernel.org/ + $ git branch --no-merged pu - - Fetch html and man branches back from k.org, and push four - integration branches and the two documentation branches to - repo.or.cz + to see there is no unexpected leftover topics. + At this point, build-test the result for semantic conflicts, and + if there are, prepare an appropriate merge-fix first (see + appendix), and rebuild the 'pu' branch from scratch, starting at + the tip of 'jch'. + + - Update "What's cooking" message to review the updates to + existing topics, newly added topics and graduated topics. + + This step is helped with Meta/cook script. + + $ Meta/cook + + This script inspects the history between master..pu, finds tips + of topic branches, compares what it found with the current + contents in Meta/whats-cooking.txt, and updates that file. + Topics not listed in the file but are found in master..pu are + added to the "New topics" section, topics listed in the file that + are no longer found in master..pu are moved to the "Graduated to + master" section, and topics whose commits changed their states + (e.g. used to be only in 'pu', now merged to 'next') are updated + with change markers "<<" and ">>". + + Look for lines enclosed in "<<" and ">>"; they hold contents from + old file that are replaced by this integration round. After + verifying them, remove the old part. Review the description for + each topic and update its doneness and plan as needed. To review + the updated plan, run + + $ Meta/cook -w + + which will pick up comments given to the topics, such as "Will + merge to 'next'", etc. (see Meta/cook script to learn what kind + of phrases are supported). + + - Compile, test and install all four (five) integration branches; + Meta/Dothem script may aid this step. + + - Format documentation if the 'master' branch was updated; + Meta/dodoc.sh script may aid this step. + + - Push the integration branches out to public places; Meta/pushall + script may aid this step. + +Observations +------------ Some observations to be made. - * Each topic is tested individually, and also together with - other topics cooking in 'next'. Until it matures, none part - of it is merged to 'master'. + * Each topic is tested individually, and also together with other + topics cooking first in 'pu', then in 'jch' and then in 'next'. + Until it matures, no part of it is merged to 'master'. * A topic already in 'next' can get fixes while still in 'next'. Such a topic will have many merges to 'next' (in other words, "git log --first-parent next" will show many - "Merge ai/topic to next" for the same topic. + "Merge branch 'ai/topic' to next" for the same topic. * An unobvious fix for 'maint' is cooked in 'next' and then merged to 'master' to make extra sure it is Ok and then @@ -275,3 +370,80 @@ Some observations to be made. * Being in the 'next' branch is not a guarantee for a topic to be included in the next feature release. Being in the 'master' branch typically is. + + +Appendix +-------- + +Preparing a "merge-fix" +~~~~~~~~~~~~~~~~~~~~~~~ + +A merge of two topics may not textually conflict but still have +conflict at the semantic level. A classic example is for one topic +to rename an variable and all its uses, while another topic adds a +new use of the variable under its old name. When these two topics +are merged together, the reference to the variable newly added by +the latter topic will still use the old name in the result. + +The Meta/Reintegrate script that is used by redo-jch and redo-pu +scripts implements a crude but usable way to work this issue around. +When the script merges branch $X, it checks if "refs/merge-fix/$X" +exists, and if so, the effect of it is squashed into the result of +the mechanical merge. In other words, + + $ echo $X | Meta/Reintegrate + +is roughly equivalent to this sequence: + + $ git merge --rerere-autoupdate $X + $ git commit + $ git cherry-pick -n refs/merge-fix/$X + $ git commit --amend + +The goal of this "prepare a merge-fix" step is to come up with a +commit that can be squashed into a result of mechanical merge to +correct semantic conflicts. + +After finding that the result of merging branch "ai/topic" to an +integration branch had such a semantic conflict, say pu~4, check the +problematic merge out on a detached HEAD, edit the working tree to +fix the semantic conflict, and make a separate commit to record the +fix-up: + + $ git checkout pu~4 + $ git show -s --pretty=%s ;# double check + Merge branch 'ai/topic' to pu + $ edit + $ git commit -m 'merge-fix/ai/topic' -a + +Then make a reference "refs/merge-fix/ai/topic" to point at this +result: + + $ git update-ref refs/merge-fix/ai/topic HEAD + +Then double check the result by asking Meta/Reintegrate to redo the +merge: + + $ git checkout pu~5 ;# the parent of the problem merge + $ echo ai/topic | Meta/Reintegrate + $ git diff pu~4 + +This time, because you prepared refs/merge-fix/ai/topic, the +resulting merge should have been tweaked to include the fix for the +semantic conflict. + +Note that this assumes that the order in which conflicting branches +are merged does not change. If the reason why merging ai/topic +branch needs this merge-fix is because another branch merged earlier +to the integration branch changed the underlying assumption ai/topic +branch made (e.g. ai/topic branch added a site to refer to a +variable, while the other branch renamed that variable and adjusted +existing use sites), and if you changed redo-jch (or redo-pu) script +to merge ai/topic branch before the other branch, then the above +merge-fix should not be applied while merging ai/topic, but should +instead be applied while merging the other branch. You would need +to move the fix to apply to the other branch, perhaps like this: + + $ mf=refs/merge-fix + $ git update-ref $mf/$the_other_branch $mf/ai/topic + $ git update-ref -d $mf/ai/topic diff --git a/Documentation/howto/new-command.txt b/Documentation/howto/new-command.txt new file mode 100644 index 0000000000..d7de5a3e9e --- /dev/null +++ b/Documentation/howto/new-command.txt @@ -0,0 +1,104 @@ +From: Eric S. Raymond <esr@thyrsus.com> +Abstract: This is how-to documentation for people who want to add extension + commands to Git. It should be read alongside api-builtin.txt. +Content-type: text/asciidoc + +How to integrate new subcommands +================================ + +This is how-to documentation for people who want to add extension +commands to Git. It should be read alongside api-builtin.txt. + +Runtime environment +------------------- + +Git subcommands are standalone executables that live in the Git exec +path, normally /usr/lib/git-core. The git executable itself is a +thin wrapper that knows where the subcommands live, and runs them by +passing command-line arguments to them. + +(If "git foo" is not found in the Git exec path, the wrapper +will look in the rest of your $PATH for it. Thus, it's possible +to write local Git extensions that don't live in system space.) + +Implementation languages +------------------------ + +Most subcommands are written in C or shell. A few are written in +Perl. + +While we strongly encourage coding in portable C for portability, +these specific scripting languages are also acceptable. We won't +accept more without a very strong technical case, as we don't want +to broaden the Git suite's required dependencies. Import utilities, +surgical tools, remote helpers and other code at the edges of the +Git suite are more lenient and we allow Python (and even Tcl/tk), +but they should not be used for core functions. + +This may change in the future. Especially Python is not allowed in +core because we need better Python integration in the Git Windows +installer before we can be confident people in that environment +won't experience an unacceptably large loss of capability. + +C commands are normally written as single modules, named after the +command, that link a collection of functions called libgit. Thus, +your command 'git-foo' would normally be implemented as a single +"git-foo.c" (or "builtin/foo.c" if it is to be linked to the main +binary); this organization makes it easy for people reading the code +to find things. + +See the CodingGuidelines document for other guidance on what we consider +good practice in C and shell, and api-builtin.txt for the support +functions available to built-in commands written in C. + +What every extension command needs +---------------------------------- + +You must have a man page, written in asciidoc (this is what Git help +followed by your subcommand name will display). Be aware that there is +a local asciidoc configuration and macros which you should use. It's +often helpful to start by cloning an existing page and replacing the +text content. + +You must have a test, written to report in TAP (Test Anything Protocol). +Tests are executables (usually shell scripts) that live in the 't' +subdirectory of the tree. Each test name begins with 't' and a sequence +number that controls where in the test sequence it will be executed; +conventionally the rest of the name stem is that of the command +being tested. + +Read the file t/README to learn more about the conventions to be used +in writing tests, and the test support library. + +Integrating a command +--------------------- + +Here are the things you need to do when you want to merge a new +subcommand into the Git tree. + +1. Don't forget to sign off your patch! + +2. Append your command name to one of the variables BUILTIN_OBJS, +EXTRA_PROGRAMS, SCRIPT_SH, SCRIPT_PERL or SCRIPT_PYTHON. + +3. Drop its test in the t directory. + +4. If your command is implemented in an interpreted language with a +p-code intermediate form, make sure .gitignore in the main directory +includes a pattern entry that ignores such files. Python .pyc and +.pyo files will already be covered. + +5. If your command has any dependency on a particular version of +your language, document it in the INSTALL file. + +6. There is a file command-list.txt in the distribution main directory +that categorizes commands by type, so they can be listed in appropriate +subsections in the documentation's summary command list. Add an entry +for yours. To understand the categories, look at git-commands.txt +in the main directory. + +7. Give the maintainer one paragraph to include in the RelNotes file +to describe the new feature; a good place to do so is in the cover +letter [PATCH 0/n]. + +That's all there is to it. diff --git a/Documentation/howto/rebase-from-internal-branch.txt b/Documentation/howto/rebase-from-internal-branch.txt index 74a1c0c4ba..02cb5f758d 100644 --- a/Documentation/howto/rebase-from-internal-branch.txt +++ b/Documentation/howto/rebase-from-internal-branch.txt @@ -4,11 +4,16 @@ Cc: Petr Baudis <pasky@suse.cz>, Linus Torvalds <torvalds@osdl.org> Subject: Re: sending changesets from the middle of a git tree Date: Sun, 14 Aug 2005 18:37:39 -0700 Abstract: In this article, JC talks about how he rebases the - public "pu" branch using the core GIT tools when he updates + public "pu" branch using the core Git tools when he updates the "master" branch, and how "rebase" works. Also discussed is how this applies to individual developers who sends patches upstream. +Content-type: text/asciidoc +How to rebase from an internal branch +===================================== + +-------------------------------------- Petr Baudis <pasky@suse.cz> writes: > Dear diary, on Sun, Aug 14, 2005 at 09:57:13AM CEST, I got a letter @@ -19,13 +24,14 @@ Petr Baudis <pasky@suse.cz> writes: >> > branch to the real branches. >> > Actually, wouldn't this be also precisely for what StGIT is intended to? +-------------------------------------- Exactly my feeling. I was sort of waiting for Catalin to speak up. With its basing philosophical ancestry on quilt, this is the kind of task StGIT is designed to do. I just have done a simpler one, this time using only the core -GIT tools. +Git tools. I had a handful of commits that were ahead of master in pu, and I wanted to add some documentation bypassing my usual habit of @@ -90,7 +96,7 @@ you ran fsck-cache, which is normal. After testing "pu", you can run "git prune" to get rid of those original three commits. While I am talking about "git rebase", I should talk about how -to do cherrypicking using only the core GIT tools. +to do cherrypicking using only the core Git tools. Let's go back to the earlier picture, with different labels. @@ -133,7 +139,7 @@ You fetch from upstream, but not merge. $ git fetch upstream This leaves the updated upstream head in .git/FETCH_HEAD but -does not touch your .git/HEAD nor .git/refs/heads/master. +does not touch your .git/HEAD or .git/refs/heads/master. You run "git rebase" now. $ git rebase FETCH_HEAD master @@ -156,8 +162,3 @@ you continue on starting from the new "master" head, which is the #1' commit. -jc - -- -To unsubscribe from this list: send the line "unsubscribe git" in -the body of a message to majordomo@vger.kernel.org -More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/Documentation/howto/rebuild-from-update-hook.txt b/Documentation/howto/rebuild-from-update-hook.txt index 48c67568d3..25378f68d3 100644 --- a/Documentation/howto/rebuild-from-update-hook.txt +++ b/Documentation/howto/rebuild-from-update-hook.txt @@ -3,19 +3,23 @@ Message-ID: <7vy86o6usx.fsf@assigned-by-dhcp.cox.net> From: Junio C Hamano <gitster@pobox.com> Date: Fri, 26 Aug 2005 18:19:10 -0700 Abstract: In this how-to article, JC talks about how he - uses the post-update hook to automate git documentation page + uses the post-update hook to automate Git documentation page shown at http://www.kernel.org/pub/software/scm/git/docs/. +Content-type: text/asciidoc + +How to rebuild from update hook +=============================== The pages under http://www.kernel.org/pub/software/scm/git/docs/ are built from Documentation/ directory of the git.git project and needed to be kept up-to-date. The www.kernel.org/ servers are mirrored and I was told that the origin of the mirror is on the machine $some.kernel.org, on which I was given an account -when I took over git maintainership from Linus. +when I took over Git maintainership from Linus. The directories relevant to this how-to are these two: - /pub/scm/git/git.git/ The public git repository. + /pub/scm/git/git.git/ The public Git repository. /pub/software/scm/git/docs/ The HTML documentation page. So I made a repository to generate the documentation under my @@ -42,7 +46,7 @@ script: EOF Initially I used to run this by hand whenever I push into the -public git repository. Then I did a cron job that ran twice a +public Git repository. Then I did a cron job that ran twice a day. The current round uses the post-update hook mechanism, like this: diff --git a/Documentation/howto/recover-corrupted-blob-object.txt b/Documentation/howto/recover-corrupted-blob-object.txt index 323b513ed0..1b3b188d3c 100644 --- a/Documentation/howto/recover-corrupted-blob-object.txt +++ b/Documentation/howto/recover-corrupted-blob-object.txt @@ -3,18 +3,24 @@ From: Linus Torvalds <torvalds@linux-foundation.org> Subject: corrupt object on git-gc Abstract: Some tricks to reconstruct blob objects in order to fix a corrupted repository. +Content-type: text/asciidoc +How to recover a corrupted blob object +====================================== + +----------------------------------------------------------- On Fri, 9 Nov 2007, Yossi Leybovich wrote: > > Did not help still the repository look for this object? > Any one know how can I track this object and understand which file is it +----------------------------------------------------------- -So exactly *because* the SHA1 hash is cryptographically secure, the hash +So exactly *because* the SHA-1 hash is cryptographically secure, the hash itself doesn't actually tell you anything, in order to fix a corrupt object you basically have to find the "original source" for it. The easiest way to do that is almost always to have backups, and find the -same object somewhere else. Backups really are a good idea, and git makes +same object somewhere else. Backups really are a good idea, and Git makes it pretty easy (if nothing else, just clone the repository somewhere else, and make sure that you do *not* use a hard-linked clone, and preferably not the same disk/machine). @@ -31,19 +37,23 @@ original object, so right now the corrupt object is useless, but it's very interesting for the future, in the hope that you can re-create a non-corrupt version. +----------------------------------------------------------- So: > ib]$ mv .git/objects/4b/9458b3786228369c63936db65827de3cc06200 ../ +----------------------------------------------------------- This is the right thing to do, although it's usually best to save it under -it's full SHA1 name (you just dropped the "4b" from the result ;). +it's full SHA-1 name (you just dropped the "4b" from the result ;). Let's see what that tells us: +----------------------------------------------------------- > ib]$ git-fsck --full > broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 > to blob 4b9458b3786228369c63936db65827de3cc06200 > missing blob 4b9458b3786228369c63936db65827de3cc06200 +----------------------------------------------------------- Ok, I removed the "dangling commit" messages, because they are just messages about the fact that you probably have rebased etc, so they're not @@ -79,7 +89,7 @@ working tree, in which case fixing this problem is really simple, just do git hash-object -w my-magic-file -again, and if it outputs the missing SHA1 (4b945..) you're now all done! +again, and if it outputs the missing SHA-1 (4b945..) you're now all done! But that's the really lucky case, so let's assume that it was some older version that was broken. How do you tell which version it was? @@ -124,7 +134,7 @@ and your repository is good again! git log --raw --all and just looked for the sha of the missing object (4b9458b..) in that -whole thing. It's up to you - git does *have* a lot of information, it is +whole thing. It's up to you - Git does *have* a lot of information, it is just missing one particular blob version. Trying to recreate trees and especially commits is *much* harder. So you diff --git a/Documentation/howto/recover-corrupted-object-harder.txt b/Documentation/howto/recover-corrupted-object-harder.txt new file mode 100644 index 0000000000..9c4cd0915f --- /dev/null +++ b/Documentation/howto/recover-corrupted-object-harder.txt @@ -0,0 +1,479 @@ +Date: Wed, 16 Oct 2013 04:34:01 -0400 +From: Jeff King <peff@peff.net> +Subject: pack corruption post-mortem +Abstract: Recovering a corrupted object when no good copy is available. +Content-type: text/asciidoc + +How to recover an object from scratch +===================================== + +I was recently presented with a repository with a corrupted packfile, +and was asked if the data was recoverable. This post-mortem describes +the steps I took to investigate and fix the problem. I thought others +might find the process interesting, and it might help somebody in the +same situation. + +******************************** +Note: In this case, no good copy of the repository was available. For +the much easier case where you can get the corrupted object from +elsewhere, see link:recover-corrupted-blob-object.html[this howto]. +******************************** + +I started with an fsck, which found a problem with exactly one object +(I've used $pack and $obj below to keep the output readable, and also +because I'll refer to them later): + +----------- + $ git fsck + error: $pack SHA1 checksum mismatch + error: index CRC mismatch for object $obj from $pack at offset 51653873 + error: inflate: data stream error (incorrect data check) + error: cannot unpack $obj from $pack at offset 51653873 +----------- + +The pack checksum failing means a byte is munged somewhere, and it is +presumably in the object mentioned (since both the index checksum and +zlib were failing). + +Reading the zlib source code, I found that "incorrect data check" means +that the adler-32 checksum at the end of the zlib data did not match the +inflated data. So stepping the data through zlib would not help, as it +did not fail until the very end, when we realize the CRC does not match. +The problematic bytes could be anywhere in the object data. + +The first thing I did was pull the broken data out of the packfile. I +needed to know how big the object was, which I found out with: + +------------ + $ git show-index <$idx | cut -d' ' -f1 | sort -n | grep -A1 51653873 + 51653873 + 51664736 +------------ + +Show-index gives us the list of objects and their offsets. We throw away +everything but the offsets, and then sort them so that our interesting +offset (which we got from the fsck output above) is followed immediately +by the offset of the next object. Now we know that the object data is +10863 bytes long, and we can grab it with: + +------------ + dd if=$pack of=object bs=1 skip=51653873 count=10863 +------------ + +I inspected a hexdump of the data, looking for any obvious bogosity +(e.g., a 4K run of zeroes would be a good sign of filesystem +corruption). But everything looked pretty reasonable. + +Note that the "object" file isn't fit for feeding straight to zlib; it +has the git packed object header, which is variable-length. We want to +strip that off so we can start playing with the zlib data directly. You +can either work your way through it manually (the format is described in +link:../technical/pack-format.html[Documentation/technical/pack-format.txt]), +or you can walk through it in a debugger. I did the latter, creating a +valid pack like: + +------------ + # pack magic and version + printf 'PACK\0\0\0\2' >tmp.pack + # pack has one object + printf '\0\0\0\1' >>tmp.pack + # now add our object data + cat object >>tmp.pack + # and then append the pack trailer + /path/to/git.git/test-sha1 -b <tmp.pack >trailer + cat trailer >>tmp.pack +------------ + +and then running "git index-pack tmp.pack" in the debugger (stop at +unpack_raw_entry). Doing this, I found that there were 3 bytes of header +(and the header itself had a sane type and size). So I stripped those +off with: + +------------ + dd if=object of=zlib bs=1 skip=3 +------------ + +I ran the result through zlib's inflate using a custom C program. And +while it did report the error, I did get the right number of output +bytes (i.e., it matched git's size header that we decoded above). But +feeding the result back to "git hash-object" didn't produce the same +sha1. So there were some wrong bytes, but I didn't know which. The file +happened to be C source code, so I hoped I could notice something +obviously wrong with it, but I didn't. I even got it to compile! + +I also tried comparing it to other versions of the same path in the +repository, hoping that there would be some part of the diff that didn't +make sense. Unfortunately, this happened to be the only revision of this +particular file in the repository, so I had nothing to compare against. + +So I took a different approach. Working under the guess that the +corruption was limited to a single byte, I wrote a program to munge each +byte individually, and try inflating the result. Since the object was +only 10K compressed, that worked out to about 2.5M attempts, which took +a few minutes. + +The program I used is here: + +---------------------------------------------- +#include <stdio.h> +#include <unistd.h> +#include <string.h> +#include <signal.h> +#include <zlib.h> + +static int try_zlib(unsigned char *buf, int len) +{ + /* make this absurdly large so we don't have to loop */ + static unsigned char out[1024*1024]; + z_stream z; + int ret; + + memset(&z, 0, sizeof(z)); + inflateInit(&z); + + z.next_in = buf; + z.avail_in = len; + z.next_out = out; + z.avail_out = sizeof(out); + + ret = inflate(&z, 0); + inflateEnd(&z); + return ret >= 0; +} + +/* eye candy */ +static int counter = 0; +static void progress(int sig) +{ + fprintf(stderr, "\r%d", counter); + alarm(1); +} + +int main(void) +{ + /* oversized so we can read the whole buffer in */ + unsigned char buf[1024*1024]; + int len; + unsigned i, j; + + signal(SIGALRM, progress); + alarm(1); + + len = read(0, buf, sizeof(buf)); + for (i = 0; i < len; i++) { + unsigned char c = buf[i]; + for (j = 0; j <= 0xff; j++) { + buf[i] = j; + + counter++; + if (try_zlib(buf, len)) + printf("i=%d, j=%x\n", i, j); + } + buf[i] = c; + } + + alarm(0); + fprintf(stderr, "\n"); + return 0; +} +---------------------------------------------- + +I compiled and ran with: + +------- + gcc -Wall -Werror -O3 munge.c -o munge -lz + ./munge <zlib +------- + + +There were a few false positives early on (if you write "no data" in the +zlib header, zlib thinks it's just fine :) ). But I got a hit about +halfway through: + +------- + i=5642, j=c7 +------- + +I let it run to completion, and got a few more hits at the end (where it +was munging the CRC to match our broken data). So there was a good +chance this middle hit was the source of the problem. + +I confirmed by tweaking the byte in a hex editor, zlib inflating the +result (no errors!), and then piping the output into "git hash-object", +which reported the sha1 of the broken object. Success! + +I fixed the packfile itself with: + +------- + chmod +w $pack + printf '\xc7' | dd of=$pack bs=1 seek=51659518 conv=notrunc + chmod -w $pack +------- + +The `\xc7` comes from the replacement byte our "munge" program found. +The offset 51659518 is derived by taking the original object offset +(51653873), adding the replacement offset found by "munge" (5642), and +then adding back in the 3 bytes of git header we stripped. + +After that, "git fsck" ran clean. + +As for the corruption itself, I was lucky that it was indeed a single +byte. In fact, it turned out to be a single bit. The byte 0xc7 was +corrupted to 0xc5. So presumably it was caused by faulty hardware, or a +cosmic ray. + +And the aborted attempt to look at the inflated output to see what was +wrong? I could have looked forever and never found it. Here's the diff +between what the corrupted data inflates to, versus the real data: + +-------------- + - cp = strtok (arg, "+"); + + cp = strtok (arg, "."); +-------------- + +It tweaked one byte and still ended up as valid, readable C that just +happened to do something totally different! One takeaway is that on a +less unlucky day, looking at the zlib output might have actually been +helpful, as most random changes would actually break the C code. + +But more importantly, git's hashing and checksumming noticed a problem +that easily could have gone undetected in another system. The result +still compiled, but would have caused an interesting bug (that would +have been blamed on some random commit). + + +The adventure continues... +-------------------------- + +I ended up doing this again! Same entity, new hardware. The assumption +at this point is that the old disk corrupted the packfile, and then the +corruption was migrated to the new hardware (because it was done by +rsync or similar, and no fsck was done at the time of migration). + +This time, the affected blob was over 20 megabytes, which was far too +large to do a brute-force on. I followed the instructions above to +create the `zlib` file. I then used the `inflate` program below to pull +the corrupted data from that. Examining that output gave me a hint about +where in the file the corruption was. But now I was working with the +file itself, not the zlib contents. So knowing the sha1 of the object +and the approximate area of the corruption, I used the `sha1-munge` +program below to brute-force the correct byte. + +Here's the inflate program (it's essentially `gunzip` but without the +`.gz` header processing): + +-------------------------- +#include <stdio.h> +#include <string.h> +#include <zlib.h> +#include <stdlib.h> + +int main(int argc, char **argv) +{ + /* + * oversized so we can read the whole buffer in; + * this could actually be switched to streaming + * to avoid any memory limitations + */ + static unsigned char buf[25 * 1024 * 1024]; + static unsigned char out[25 * 1024 * 1024]; + int len; + z_stream z; + int ret; + + len = read(0, buf, sizeof(buf)); + memset(&z, 0, sizeof(z)); + inflateInit(&z); + + z.next_in = buf; + z.avail_in = len; + z.next_out = out; + z.avail_out = sizeof(out); + + ret = inflate(&z, 0); + if (ret != Z_OK && ret != Z_STREAM_END) + fprintf(stderr, "initial inflate failed (%d)\n", ret); + + fprintf(stderr, "outputting %lu bytes", z.total_out); + fwrite(out, 1, z.total_out, stdout); + return 0; +} +-------------------------- + +And here is the `sha1-munge` program: + +-------------------------- +#include <stdio.h> +#include <unistd.h> +#include <string.h> +#include <signal.h> +#include <openssl/sha.h> +#include <stdlib.h> + +/* eye candy */ +static int counter = 0; +static void progress(int sig) +{ + fprintf(stderr, "\r%d", counter); + alarm(1); +} + +static const signed char hexval_table[256] = { + -1, -1, -1, -1, -1, -1, -1, -1, /* 00-07 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 08-0f */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 10-17 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 18-1f */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 20-27 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 28-2f */ + 0, 1, 2, 3, 4, 5, 6, 7, /* 30-37 */ + 8, 9, -1, -1, -1, -1, -1, -1, /* 38-3f */ + -1, 10, 11, 12, 13, 14, 15, -1, /* 40-47 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 48-4f */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 50-57 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 58-5f */ + -1, 10, 11, 12, 13, 14, 15, -1, /* 60-67 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 68-67 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 70-77 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 78-7f */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 80-87 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 88-8f */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 90-97 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* 98-9f */ + -1, -1, -1, -1, -1, -1, -1, -1, /* a0-a7 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* a8-af */ + -1, -1, -1, -1, -1, -1, -1, -1, /* b0-b7 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* b8-bf */ + -1, -1, -1, -1, -1, -1, -1, -1, /* c0-c7 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* c8-cf */ + -1, -1, -1, -1, -1, -1, -1, -1, /* d0-d7 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* d8-df */ + -1, -1, -1, -1, -1, -1, -1, -1, /* e0-e7 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* e8-ef */ + -1, -1, -1, -1, -1, -1, -1, -1, /* f0-f7 */ + -1, -1, -1, -1, -1, -1, -1, -1, /* f8-ff */ +}; + +static inline unsigned int hexval(unsigned char c) +{ +return hexval_table[c]; +} + +static int get_sha1_hex(const char *hex, unsigned char *sha1) +{ + int i; + for (i = 0; i < 20; i++) { + unsigned int val; + /* + * hex[1]=='\0' is caught when val is checked below, + * but if hex[0] is NUL we have to avoid reading + * past the end of the string: + */ + if (!hex[0]) + return -1; + val = (hexval(hex[0]) << 4) | hexval(hex[1]); + if (val & ~0xff) + return -1; + *sha1++ = val; + hex += 2; + } + return 0; +} + +int main(int argc, char **argv) +{ + /* oversized so we can read the whole buffer in */ + static unsigned char buf[25 * 1024 * 1024]; + char header[32]; + int header_len; + unsigned char have[20], want[20]; + int start, len; + SHA_CTX orig; + unsigned i, j; + + if (!argv[1] || get_sha1_hex(argv[1], want)) { + fprintf(stderr, "usage: sha1-munge <sha1> [start] <file.in\n"); + return 1; + } + + if (argv[2]) + start = atoi(argv[2]); + else + start = 0; + + len = read(0, buf, sizeof(buf)); + header_len = sprintf(header, "blob %d", len) + 1; + fprintf(stderr, "using header: %s\n", header); + + /* + * We keep a running sha1 so that if you are munging + * near the end of the file, we do not have to re-sha1 + * the unchanged earlier bytes + */ + SHA1_Init(&orig); + SHA1_Update(&orig, header, header_len); + if (start) + SHA1_Update(&orig, buf, start); + + signal(SIGALRM, progress); + alarm(1); + + for (i = start; i < len; i++) { + unsigned char c; + SHA_CTX x; + +#if 0 + /* + * deletion -- this would not actually work in practice, + * I think, because we've already committed to a + * particular size in the header. Ditto for addition + * below. In those cases, you'd have to do the whole + * sha1 from scratch, or possibly keep three running + * "orig" sha1 computations going. + */ + memcpy(&x, &orig, sizeof(x)); + SHA1_Update(&x, buf + i + 1, len - i - 1); + SHA1_Final(have, &x); + if (!memcmp(have, want, 20)) + printf("i=%d, deletion\n", i); +#endif + + /* + * replacement -- note that this tries each of the 256 + * possible bytes. If you suspect a single-bit flip, + * it would be much shorter to just try the 8 + * bit-flipped variants. + */ + c = buf[i]; + for (j = 0; j <= 0xff; j++) { + buf[i] = j; + + memcpy(&x, &orig, sizeof(x)); + SHA1_Update(&x, buf + i, len - i); + SHA1_Final(have, &x); + if (!memcmp(have, want, 20)) + printf("i=%d, j=%02x\n", i, j); + } + buf[i] = c; + +#if 0 + /* addition */ + for (j = 0; j <= 0xff; j++) { + unsigned char extra = j; + memcpy(&x, &orig, sizeof(x)); + SHA1_Update(&x, &extra, 1); + SHA1_Update(&x, buf + i, len - i); + SHA1_Final(have, &x); + if (!memcmp(have, want, 20)) + printf("i=%d, addition=%02x", i, j); + } +#endif + + SHA1_Update(&orig, buf + i, 1); + counter++; + } + + alarm(0); + fprintf(stderr, "\r%d\n", counter); + return 0; +} +-------------------------- diff --git a/Documentation/howto/revert-a-faulty-merge.txt b/Documentation/howto/revert-a-faulty-merge.txt index 3b4a390005..462255ed5d 100644 --- a/Documentation/howto/revert-a-faulty-merge.txt +++ b/Documentation/howto/revert-a-faulty-merge.txt @@ -7,6 +7,10 @@ Abstract: Sometimes a branch that was already merged to the mainline after the offending branch is fixed. Message-ID: <7vocz8a6zk.fsf@gitster.siamese.dyndns.org> References: <alpine.LFD.2.00.0812181949450.14014@localhost.localdomain> +Content-type: text/asciidoc + +How to revert a faulty merge +============================ Alan <alan@clueserver.org> said: @@ -33,7 +37,7 @@ where A and B are on the side development that was not so good, M is the merge that brings these premature changes into the mainline, x are changes unrelated to what the side branch did and already made on the mainline, and W is the "revert of the merge M" (doesn't W look M upside down?). -IOW, "diff W^..W" is similar to "diff -R M^..M". +IOW, `"diff W^..W"` is similar to `"diff -R M^..M"`. Such a "revert" of a merge can be made with: @@ -50,7 +54,7 @@ where C and D are to fix what was broken in A and B, and you may already have some other changes on the mainline after W. If you merge the updated side branch (with D at its tip), none of the -changes made in A nor B will be in the result, because they were reverted +changes made in A or B will be in the result, because they were reverted by W. That is what Alan saw. Linus explains the situation: @@ -86,7 +90,7 @@ with: $ git revert W This history would (ignoring possible conflicts between what W and W..Y -changed) be equivalent to not having W nor Y at all in the history: +changed) be equivalent to not having W or Y at all in the history: ---o---o---o---M---x---x-------x---- / @@ -117,9 +121,9 @@ If you reverted the revert in such a case as in the previous example: ---A---B A'--B'--C' where Y is the revert of W, A' and B' are rerolled A and B, and there may -also be a further fix-up C' on the side branch. "diff Y^..Y" is similar -to "diff -R W^..W" (which in turn means it is similar to "diff M^..M"), -and "diff A'^..C'" by definition would be similar but different from that, +also be a further fix-up C' on the side branch. `"diff Y^..Y"` is similar +to `"diff -R W^..W"` (which in turn means it is similar to `"diff M^..M"`), +and `"diff A'^..C'"` by definition would be similar but different from that, because it is a rerolled series of the earlier change. There will be a lot of overlapping changes that result in conflicts. So do not do "revert of revert" blindly without thinking.. @@ -142,6 +146,8 @@ different resolution strategies: revert of a merge was rebuilt from scratch (i.e. rebasing and fixing, as you seem to have interpreted), then re-merging the result without doing anything else fancy would be the right thing to do. + (See the ADDENDUM below for how to rebuild a branch from scratch + without changing its original branching-off point.) However, there are things to keep in mind when reverting a merge (and reverting such a revert). @@ -158,7 +164,7 @@ merged. So it's debugging hell, because now you don't have lots of small changes that you can try to pinpoint which _part_ of it changes. But does it all work? Sure it does. You can revert a merge, and from a -purely technical angle, git did it very naturally and had no real +purely technical angle, Git did it very naturally and had no real troubles. It just considered it a change from "state before merge" to "state after merge", and that was it. Nothing complicated, nothing odd, nothing really dangerous. Git will do it without even thinking about it. @@ -177,3 +183,91 @@ the answer is: "oops, I really shouldn't have merged it, because it wasn't ready yet, and I really need to undo _all_ of the merge"). So then you really should revert the merge, but when you want to re-do the merge, you now need to do it by reverting the revert. + +ADDENDUM + +Sometimes you have to rewrite one of a topic branch's commits *and* you can't +change the topic's branching-off point. Consider the following situation: + + P---o---o---M---x---x---W---x + \ / + A---B---C + +where commit W reverted commit M because it turned out that commit B was wrong +and needs to be rewritten, but you need the rewritten topic to still branch +from commit P (perhaps P is a branching-off point for yet another branch, and +you want be able to merge the topic into both branches). + +The natural thing to do in this case is to checkout the A-B-C branch and use +"rebase -i P" to change commit B. However this does not rewrite commit A, +because "rebase -i" by default fast-forwards over any initial commits selected +with the "pick" command. So you end up with this: + + P---o---o---M---x---x---W---x + \ / + A---B---C <-- old branch + \ + B'---C' <-- naively rewritten branch + +To merge A-B'-C' into the mainline branch you would still have to first revert +commit W in order to pick up the changes in A, but then it's likely that the +changes in B' will conflict with the original B changes re-introduced by the +reversion of W. + +However, you can avoid these problems if you recreate the entire branch, +including commit A: + + A'---B'---C' <-- completely rewritten branch + / + P---o---o---M---x---x---W---x + \ / + A---B---C + +You can merge A'-B'-C' into the mainline branch without worrying about first +reverting W. Mainline's history would look like this: + + A'---B'---C'------------------ + / \ + P---o---o---M---x---x---W---x---M2 + \ / + A---B---C + +But if you don't actually need to change commit A, then you need some way to +recreate it as a new commit with the same changes in it. The rebase command's +--no-ff option provides a way to do this: + + $ git rebase [-i] --no-ff P + +The --no-ff option creates a new branch A'-B'-C' with all-new commits (all the +SHA IDs will be different) even if in the interactive case you only actually +modify commit B. You can then merge this new branch directly into the mainline +branch and be sure you'll get all of the branch's changes. + +You can also use --no-ff in cases where you just add extra commits to the topic +to fix it up. Let's revisit the situation discussed at the start of this howto: + + P---o---o---M---x---x---W---x + \ / + A---B---C----------------D---E <-- fixed-up topic branch + +At this point, you can use --no-ff to recreate the topic branch: + + $ git checkout E + $ git rebase --no-ff P + +yielding + + A'---B'---C'------------D'---E' <-- recreated topic branch + / + P---o---o---M---x---x---W---x + \ / + A---B---C----------------D---E + +You can merge the recreated branch into the mainline without reverting commit W, +and mainline's history will look like this: + + A'---B'---C'------------D'---E' + / \ + P---o---o---M---x---x---W---x---M2 + \ / + A---B---C diff --git a/Documentation/howto/revert-branch-rebase.txt b/Documentation/howto/revert-branch-rebase.txt index e70d8a31e7..149508e13b 100644 --- a/Documentation/howto/revert-branch-rebase.txt +++ b/Documentation/howto/revert-branch-rebase.txt @@ -8,14 +8,14 @@ Date: Mon, 29 Aug 2005 21:39:02 -0700 Content-type: text/asciidoc Message-ID: <7voe7g3uop.fsf@assigned-by-dhcp.cox.net> -Reverting an existing commit -============================ +How to revert an existing commit +================================ One of the changes I pulled into the 'master' branch turns out to -break building GIT with GCC 2.95. While they were well intentioned +break building Git with GCC 2.95. While they were well-intentioned portability fixes, keeping things working with gcc-2.95 was also important. Here is what I did to revert the change in the 'master' -branch and to adjust the 'pu' branch, using core GIT tools and +branch and to adjust the 'pu' branch, using core Git tools and barebone Porcelain. First, prepare a throw-away branch in case I screw things up. @@ -85,7 +85,7 @@ Fortunately I did not have to; what I have in the current branch ------------------------------------------------ $ git checkout master -$ git merge revert-c99 ;# this should be a fast forward +$ git merge revert-c99 ;# this should be a fast-forward Updating from 10d781b9caa4f71495c7b34963bef137216f86a8 to e3a693c... cache.h | 8 ++++---- commit.c | 2 +- @@ -95,7 +95,7 @@ Updating from 10d781b9caa4f71495c7b34963bef137216f86a8 to e3a693c... 5 files changed, 8 insertions(+), 8 deletions(-) ------------------------------------------------ -There is no need to redo the test at this point. We fast forwarded +There is no need to redo the test at this point. We fast-forwarded and we know 'master' matches 'revert-c99' exactly. In fact: ------------------------------------------------ @@ -112,25 +112,19 @@ $ git tag pu-anchor pu $ git rebase master * Applying: Redo "revert" using three-way merge machinery. First trying simple merge strategy to cherry-pick. -Finished one cherry-pick. * Applying: Remove git-apply-patch-script. First trying simple merge strategy to cherry-pick. Simple cherry-pick fails; trying Automatic cherry-pick. Removing Documentation/git-apply-patch-script.txt Removing git-apply-patch-script -Finished one cherry-pick. * Applying: Document "git cherry-pick" and "git revert" First trying simple merge strategy to cherry-pick. -Finished one cherry-pick. * Applying: mailinfo and applymbox updates First trying simple merge strategy to cherry-pick. -Finished one cherry-pick. * Applying: Show commits in topo order and name all commits. First trying simple merge strategy to cherry-pick. -Finished one cherry-pick. * Applying: More documentation updates. First trying simple merge strategy to cherry-pick. -Finished one cherry-pick. ------------------------------------------------ The temporary tag 'pu-anchor' is me just being careful, in case 'git @@ -143,7 +137,7 @@ $ make clean test ;# make sure it did not cause other breakage. ------------------------------------------------ Everything is in the good order. I do not need the temporary branch -nor tag anymore, so remove them: +or tag anymore, so remove them: ------------------------------------------------ $ rm -f .git/refs/tags/pu-anchor @@ -160,7 +154,7 @@ $ git pull . master Packing 0 objects Unpacking 0 objects -* committish: e3a693c... refs/heads/master from . +* commit-ish: e3a693c... refs/heads/master from . Trying to merge e3a693c... into 8c1f5f0... using 10d781b... Committed merge 7fb9b7262a1d1e0a47bbfdcbbcf50ce0635d3f8f cache.h | 8 ++++---- diff --git a/Documentation/howto/separating-topic-branches.txt b/Documentation/howto/separating-topic-branches.txt index 6d3eb8ed00..bd1027433b 100644 --- a/Documentation/howto/separating-topic-branches.txt +++ b/Documentation/howto/separating-topic-branches.txt @@ -1,6 +1,10 @@ From: Junio C Hamano <gitster@pobox.com> Subject: Separating topic branches Abstract: In this article, JC describes how to separate topic branches. +Content-type: text/asciidoc + +How to separate topic branches +============================== This text was originally a footnote to a discussion about the behaviour of the git diff commands. diff --git a/Documentation/howto/setup-git-server-over-http.txt b/Documentation/howto/setup-git-server-over-http.txt index 622ee5c8dd..f44e5e9458 100644 --- a/Documentation/howto/setup-git-server-over-http.txt +++ b/Documentation/howto/setup-git-server-over-http.txt @@ -1,6 +1,14 @@ From: Rutger Nijlunsing <rutger@nospam.com> -Subject: Setting up a git repository which can be pushed into and pulled from over HTTP(S). +Subject: Setting up a Git repository which can be pushed into and pulled from over HTTP(S). Date: Thu, 10 Aug 2006 22:00:26 +0200 +Content-type: text/asciidoc + +How to setup Git server over http +================================= + +NOTE: This document is from 2006. A lot has happened since then, and this +document is now relevant mainly if your web host is not CGI capable. +Almost everyone else should instead look at linkgit:git-http-backend[1]. Since Apache is one of those packages people like to compile themselves while others prefer the bureaucrat's dream Debian, it is @@ -40,20 +48,20 @@ What's needed: - have permissions to chown a directory -- have git installed on the client, and +- have Git installed on the client, and -- either have git installed on the server or have a webdav client on +- either have Git installed on the server or have a webdav client on the client. In effect, this means you're going to be root, or that you're using a preconfigured WebDAV server. -Step 1: setup a bare GIT repository +Step 1: setup a bare Git repository ----------------------------------- -At the time of writing, git-http-push cannot remotely create a GIT -repository. So we have to do that at the server side with git. Another +At the time of writing, git-http-push cannot remotely create a Git +repository. So we have to do that at the server side with Git. Another option is to generate an empty bare repository at the client and copy it to the server with a WebDAV client (which is the only option if Git is not installed on the server). @@ -77,8 +85,8 @@ Initialize a bare repository $ git --bare init -Change the ownership to your web-server's credentials. Use "grep ^User -httpd.conf" and "grep ^Group httpd.conf" to find out: +Change the ownership to your web-server's credentials. Use `"grep ^User +httpd.conf"` and `"grep ^Group httpd.conf"` to find out: $ chown -R www.www . @@ -173,7 +181,7 @@ On Debian: Most tests should pass. -A command line tool to test WebDAV is cadaver. If you prefer GUIs, for +A command-line tool to test WebDAV is cadaver. If you prefer GUIs, for example, konqueror can open WebDAV URLs as "webdav://..." or "webdavs://...". @@ -185,7 +193,7 @@ http://<servername>/my-new-repo.git [x] Open as webfolder -> login . Step 3: setup the client ------------------------ -Make sure that you have HTTP support, i.e. your git was built with +Make sure that you have HTTP support, i.e. your Git was built with libcurl (version more recent than 7.10). The command 'git http-push' with no argument should display a usage message. @@ -264,7 +272,7 @@ Reading /usr/local/apache2/logs/error_log is often helpful. On Debian: Read /var/log/apache2/error.log instead. -If you access HTTPS locations, git may fail verifying the SSL +If you access HTTPS locations, Git may fail verifying the SSL certificate (this is return code 60). Setting http.sslVerify=false can help diagnosing the problem, but removes security checks. diff --git a/Documentation/howto/update-hook-example.txt b/Documentation/howto/update-hook-example.txt index 697d918885..a5193b1e5c 100644 --- a/Documentation/howto/update-hook-example.txt +++ b/Documentation/howto/update-hook-example.txt @@ -5,6 +5,10 @@ Message-ID: <7vfypumlu3.fsf@assigned-by-dhcp.cox.net> Abstract: An example hooks/update script is presented to implement repository maintenance policies, such as who can push into which branch and who can make a tag. +Content-type: text/asciidoc + +How to use the update hook +========================== When your developer runs git-push into the repository, git-receive-pack is run (either locally or over ssh) as that @@ -32,8 +36,7 @@ like this as your hooks/update script. [jc: editorial note. This is a much improved version by Carl since I posted the original outline] --- >8 -- beginning of script -- >8 -- - +---------------------------------------------------- #!/bin/bash umask 002 @@ -76,7 +79,7 @@ case "$1" in if expr "$2" : '0*$' >/dev/null; then info "The branch '$1' is new..." else - # updating -- make sure it is a fast forward + # updating -- make sure it is a fast-forward mb=$(git-merge-base "$2" "$3") case "$mb,$2" in "$2,$mb") info "Update is fast-forward" ;; @@ -111,12 +114,12 @@ then info "Found matching head pattern: '$head_pattern'" for user_pattern in $user_patterns; do - info "Checking user: '$username' against pattern: '$user_pattern'" - matchlen=$(expr "$username" : "$user_pattern") - if test "$matchlen" = "${#username}" - then - grant "Allowing user: '$username' with pattern: '$user_pattern'" - fi + info "Checking user: '$username' against pattern: '$user_pattern'" + matchlen=$(expr "$username" : "$user_pattern") + if test "$matchlen" = "${#username}" + then + grant "Allowing user: '$username' with pattern: '$user_pattern'" + fi done deny "The user is not in the access list for this branch" done @@ -149,13 +152,13 @@ then info "Found matching head pattern: '$head_pattern'" for group_pattern in $group_patterns; do - for groupname in $groups; do - info "Checking group: '$groupname' against pattern: '$group_pattern'" - matchlen=$(expr "$groupname" : "$group_pattern") - if test "$matchlen" = "${#groupname}" - then - grant "Allowing group: '$groupname' with pattern: '$group_pattern'" - fi + for groupname in $groups; do + info "Checking group: '$groupname' against pattern: '$group_pattern'" + matchlen=$(expr "$groupname" : "$group_pattern") + if test "$matchlen" = "${#groupname}" + then + grant "Allowing group: '$groupname' with pattern: '$group_pattern'" + fi done done deny "None of the user's groups are in the access list for this branch" @@ -169,24 +172,21 @@ then fi deny >/dev/null "There are no more rules to check. Denying access" - --- >8 -- end of script -- >8 -- +---------------------------------------------------- This uses two files, $GIT_DIR/info/allowed-users and allowed-groups, to describe which heads can be pushed into by whom. The format of each file would look like this: - refs/heads/master junio - +refs/heads/pu junio - refs/heads/cogito$ pasky - refs/heads/bw/.* linus - refs/heads/tmp/.* .* - refs/tags/v[0-9].* junio + refs/heads/master junio + +refs/heads/pu junio + refs/heads/cogito$ pasky + refs/heads/bw/.* linus + refs/heads/tmp/.* .* + refs/tags/v[0-9].* junio With this, Linus can push or create "bw/penguin" or "bw/zebra" or "bw/panda" branches, Pasky can do only "cogito", and JC can do master and pu branches and make versioned tags. And anybody can do tmp/blah branches. The '+' sign at the pu record means that JC can make non-fast-forward pushes on it. - ------------- diff --git a/Documentation/howto/use-git-daemon.txt b/Documentation/howto/use-git-daemon.txt index 4e2f75cb61..7af2e52cf3 100644 --- a/Documentation/howto/use-git-daemon.txt +++ b/Documentation/howto/use-git-daemon.txt @@ -1,7 +1,10 @@ +Content-type: text/asciidoc + How to use git-daemon +===================== Git can be run in inetd mode and in stand alone mode. But all you want is -let a coworker pull from you, and therefore need to set up a git server +let a coworker pull from you, and therefore need to set up a Git server real quick, right? Note that git-daemon is not really chatty at the moment, especially when diff --git a/Documentation/howto/using-merge-subtree.txt b/Documentation/howto/using-merge-subtree.txt index 0953a50b69..1ae8d1214e 100644 --- a/Documentation/howto/using-merge-subtree.txt +++ b/Documentation/howto/using-merge-subtree.txt @@ -25,7 +25,7 @@ What you want is the 'subtree' merge strategy, which helps you in such a situation. In this example, let's say you have the repository at `/path/to/B` (but -it can be an URL as well, if you want). You want to merge the 'master' +it can be a URL as well, if you want). You want to merge the 'master' branch of that repository to the `dir-B` subdirectory in your current branch. @@ -71,5 +71,5 @@ Additional tips relevant parts of your tree. - Please note that if the other project merges from you, then it will - connects its history to yours, which can be something they don't want + connect its history to yours, which can be something they don't want to. diff --git a/Documentation/howto/using-signed-tag-in-pull-request.txt b/Documentation/howto/using-signed-tag-in-pull-request.txt new file mode 100644 index 0000000000..bbf040eda8 --- /dev/null +++ b/Documentation/howto/using-signed-tag-in-pull-request.txt @@ -0,0 +1,217 @@ +From: Junio C Hamano <gitster@pobox.com> +Date: Tue, 17 Jan 2011 13:00:00 -0800 +Subject: Using signed tag in pull requests +Abstract: Beginning v1.7.9, a contributor can push a signed tag to her + publishing repository and ask her integrator to pull it. This assures the + integrator that the pulled history is authentic and allows others to + later validate it. +Content-type: text/asciidoc + +How to use a signed tag in pull requests +======================================== + +A typical distributed workflow using Git is for a contributor to fork a +project, build on it, publish the result to her public repository, and ask +the "upstream" person (often the owner of the project where she forked +from) to pull from her public repository. Requesting such a "pull" is made +easy by the `git request-pull` command. + +Earlier, a typical pull request may have started like this: + +------------ + The following changes since commit 406da78032179...: + + Froboz 3.2 (2011-09-30 14:20:57 -0700) + + are available in the Git repository at: + + example.com:/git/froboz.git for-xyzzy +------------ + +followed by a shortlog of the changes and a diffstat. + +The request was for a branch name (e.g. `for-xyzzy`) in the public +repository of the contributor, and even though it stated where the +contributor forked her work from, the message did not say anything about +the commit to expect at the tip of the for-xyzzy branch. If the site that +hosts the public repository of the contributor cannot be fully trusted, it +was unnecessarily hard to make sure what was pulled by the integrator was +genuinely what the contributor had produced for the project. Also there +was no easy way for third-party auditors to later verify the resulting +history. + +Starting from Git release v1.7.9, a contributor can add a signed tag to +the commit at the tip of the history and ask the integrator to pull that +signed tag. When the integrator runs `git pull`, the signed tag is +automatically verified to assure that the history is not tampered with. +In addition, the resulting merge commit records the content of the signed +tag, so that other people can verify that the branch merged by the +integrator was signed by the contributor, without fetching the signed tag +used to validate the pull request separately and keeping it in the refs +namespace. + +This document describes the workflow between the contributor and the +integrator, using Git v1.7.9 or later. + + +A contributor or a lieutenant +----------------------------- + +After preparing her work to be pulled, the contributor uses `git tag -s` +to create a signed tag: + +------------ + $ git checkout work + $ ... "git pull" from sublieutenants, "git commit" your own work ... + $ git tag -s -m "Completed frotz feature" frotz-for-xyzzy work +------------ + +Note that this example uses the `-m` option to create a signed tag with +just a one-liner message, but this is for illustration purposes only. It +is advisable to compose a well-written explanation of what the topic does +to justify why it is worthwhile for the integrator to pull it, as this +message will eventually become part of the final history after the +integrator responds to the pull request (as we will see later). + +Then she pushes the tag out to her public repository: + +------------ + $ git push example.com:/git/froboz.git/ +frotz-for-xyzzy +------------ + +There is no need to push the `work` branch or anything else. + +Note that the above command line used a plus sign at the beginning of +`+frotz-for-xyzzy` to allow forcing the update of a tag, as the same +contributor may want to reuse a signed tag with the same name after the +previous pull request has already been responded to. + +The contributor then prepares a message to request a "pull": + +------------ + $ git request-pull v3.2 example.com:/git/froboz.git/ frotz-for-xyzzy >msg.txt +------------ + +The arguments are: + +. the version of the integrator's commit the contributor based her work on; +. the URL of the repository, to which the contributor has pushed what she + wants to get pulled; and +. the name of the tag the contributor wants to get pulled (earlier, she could + write only a branch name here). + +The resulting msg.txt file begins like so: + +------------ + The following changes since commit 406da78032179...: + + Froboz 3.2 (2011-09-30 14:20:57 -0700) + + are available in the Git repository at: + + example.com:/git/froboz.git tags/frotz-for-xyzzy + + for you to fetch changes up to 703f05ad5835c...: + + Add tests and documentation for frotz (2011-12-02 10:02:52 -0800) + + ----------------------------------------------- + Completed frotz feature + ----------------------------------------------- +------------ + +followed by a shortlog of the changes and a diffstat. Comparing this with +the earlier illustration of the output from the traditional `git request-pull` +command, the reader should notice that: + +. The tip commit to expect is shown to the integrator; and +. The signed tag message is shown prominently between the dashed lines + before the shortlog. + +The latter is why the contributor would want to justify why pulling her +work is worthwhile when creating the signed tag. The contributor then +opens her favorite MUA, reads msg.txt, edits and sends it to her upstream +integrator. + + +Integrator +---------- + +After receiving such a pull request message, the integrator fetches and +integrates the tag named in the request, with: + +------------ + $ git pull example.com:/git/froboz.git/ tags/frotz-for-xyzzy +------------ + +This operation will always open an editor to allow the integrator to fine +tune the commit log message when merging a signed tag. Also, pulling a +signed tag will always create a merge commit even when the integrator does +not have any new commit since the contributor's work forked (i.e. 'fast +forward'), so that the integrator can properly explain what the merge is +about and why it was made. + +In the editor, the integrator will see something like this: + +------------ + Merge tag 'frotz-for-xyzzy' of example.com:/git/froboz.git/ + + Completed frotz feature + # gpg: Signature made Fri 02 Dec 2011 10:03:01 AM PST using RSA key ID 96AFE6CB + # gpg: Good signature from "Con Tributor <nitfol@example.com>" +------------ + +Notice that the message recorded in the signed tag "Completed frotz +feature" appears here, and again that is why it is important for the +contributor to explain her work well when creating the signed tag. + +As usual, the lines commented with `#` are stripped out. The resulting +commit records the signed tag used for this validation in a hidden field +so that it can later be used by others to audit the history. There is no +need for the integrator to keep a separate copy of the tag in his +repository (i.e. `git tag -l` won't list the `frotz-for-xyzzy` tag in the +above example), and there is no need to publish the tag to his public +repository, either. + +After the integrator responds to the pull request and her work becomes +part of the permanent history, the contributor can remove the tag from +her public repository, if she chooses, in order to keep the tag namespace +of her public repository clean, with: + +------------ + $ git push example.com:/git/froboz.git :frotz-for-xyzzy +------------ + + +Auditors +-------- + +The `--show-signature` option can be given to `git log` or `git show` and +shows the verification status of the embedded signed tag in merge commits +created when the integrator responded to a pull request of a signed tag. + +A typical output from `git show --show-signature` may look like this: + +------------ + $ git show --show-signature + commit 02306ef6a3498a39118aef9df7975bdb50091585 + merged tag 'frotz-for-xyzzy' + gpg: Signature made Fri 06 Jan 2012 12:41:49 PM PST using RSA key ID 96AFE6CB + gpg: Good signature from "Con Tributor <nitfol@example.com>" + Merge: 406da78 703f05a + Author: Inte Grator <xyzzy@example.com> + Date: Tue Jan 17 13:49:41 2012 -0800 + + Merge tag 'frotz-for-xyzzy' of example.com:/git/froboz.git/ + + Completed frotz feature + + * tag 'frotz-for-xyzzy' (100 commits) + Add tests and documentation for frotz + ... +------------ + +There is no need for the auditor to explicitly fetch the contributor's +signature, or to even be aware of what tag(s) the contributor and integrator +used to communicate the signature. All the required information is recorded +as part of the merge commit. |