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 | 18 | ||||
| -rw-r--r-- | Documentation/howto/rebase-from-internal-branch.txt | 2 | ||||
| -rw-r--r-- | Documentation/howto/revert-a-faulty-merge.txt | 4 | ||||
| -rw-r--r-- | Documentation/howto/revert-branch-rebase.txt | 2 | ||||
| -rw-r--r-- | Documentation/howto/setup-git-server-over-http.txt | 2 |
6 files changed, 232 insertions, 12 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 33ae69c11f..ca4378740c 100644 --- a/Documentation/howto/maintain-git.txt +++ b/Documentation/howto/maintain-git.txt @@ -39,26 +39,26 @@ 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. - - 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. - One release cycle for a feature release is expected to last for eight to ten weeks. - - 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). + - 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 @@ -86,6 +86,10 @@ this mailing list after each feature release is made. 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 ----------------- diff --git a/Documentation/howto/rebase-from-internal-branch.txt b/Documentation/howto/rebase-from-internal-branch.txt index 19ab604f1f..02cb5f758d 100644 --- a/Documentation/howto/rebase-from-internal-branch.txt +++ b/Documentation/howto/rebase-from-internal-branch.txt @@ -139,7 +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 diff --git a/Documentation/howto/revert-a-faulty-merge.txt b/Documentation/howto/revert-a-faulty-merge.txt index acf3e477e5..462255ed5d 100644 --- a/Documentation/howto/revert-a-faulty-merge.txt +++ b/Documentation/howto/revert-a-faulty-merge.txt @@ -54,7 +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: @@ -90,7 +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---- / diff --git a/Documentation/howto/revert-branch-rebase.txt b/Documentation/howto/revert-branch-rebase.txt index 85f69dbac9..149508e13b 100644 --- a/Documentation/howto/revert-branch-rebase.txt +++ b/Documentation/howto/revert-branch-rebase.txt @@ -137,7 +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 diff --git a/Documentation/howto/setup-git-server-over-http.txt b/Documentation/howto/setup-git-server-over-http.txt index 6de4f3c487..f44e5e9458 100644 --- a/Documentation/howto/setup-git-server-over-http.txt +++ b/Documentation/howto/setup-git-server-over-http.txt @@ -181,7 +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://...". |