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Diffstat (limited to 'Documentation/git-read-tree.txt')
| -rw-r--r-- | Documentation/git-read-tree.txt | 184 |
1 files changed, 118 insertions, 66 deletions
diff --git a/Documentation/git-read-tree.txt b/Documentation/git-read-tree.txt index 4a932b08c6..fa1d557e5b 100644 --- a/Documentation/git-read-tree.txt +++ b/Documentation/git-read-tree.txt @@ -8,10 +8,11 @@ git-read-tree - Reads tree information into the index SYNOPSIS -------- +[verse] 'git read-tree' [[-m [--trivial] [--aggressive] | --reset | --prefix=<prefix>] [-u [--exclude-per-directory=<gitignore>] | -i]] - [--index-output=<file>] - <tree-ish1> [<tree-ish2> [<tree-ish3>]] + [--index-output=<file>] [--no-sparse-checkout] + (--empty | <tree-ish1> [<tree-ish2> [<tree-ish3>]]) DESCRIPTION @@ -25,8 +26,8 @@ fast-forward (i.e. 2-way) merge, or a 3-way merge, with the `-m` flag. When used with `-m`, the `-u` flag causes it to also update the files in the work tree with the result of the merge. -Trivial merges are done by 'git-read-tree' itself. Only conflicting paths -will be in unmerged state when 'git-read-tree' returns. +Trivial merges are done by 'git read-tree' itself. Only conflicting paths +will be in unmerged state when 'git read-tree' returns. OPTIONS ------- @@ -46,42 +47,46 @@ OPTIONS -i:: Usually a merge requires the index file as well as the - files in the working tree are up to date with the + files in the working tree to be up to date with the current head commit, in order not to lose local changes. This flag disables the check with the working tree and is meant to be used when creating a merge of trees that are not directly related to the current working tree status into a temporary index file. +-n:: +--dry-run:: + Check if the command would error out, without updating the index + or the files in the working tree for real. + -v:: Show the progress of checking files out. --trivial:: - Restrict three-way merge by 'git-read-tree' to happen + Restrict three-way merge by 'git read-tree' to happen only if there is no file-level merging required, instead of resolving merge for trivial cases and leaving conflicting files unresolved in the index. --aggressive:: - Usually a three-way merge by 'git-read-tree' resolves + Usually a three-way merge by 'git read-tree' resolves the merge for really trivial cases and leaves other - cases unresolved in the index, so that Porcelains can + cases unresolved in the index, so that porcelains can implement different merge policies. This flag makes the - command to resolve a few more cases internally: + command resolve a few more cases internally: + * when one side removes a path and the other side leaves the path unmodified. The resolution is to remove that path. * when both sides remove a path. The resolution is to remove that path. -* when both sides adds a path identically. The resolution +* when both sides add a path identically. The resolution is to add that path. --prefix=<prefix>/:: Keep the current index contents, and read the contents - of named tree-ish under directory at `<prefix>`. The - original index file cannot have anything at the path - `<prefix>` itself, and have nothing in `<prefix>/` - directory. Note that the `<prefix>/` value must end - with a slash. + of the named tree-ish under the directory at `<prefix>`. + The command will refuse to overwrite entries that already + existed in the original index file. Note that the `<prefix>/` + value must end with a slash. --exclude-per-directory=<gitignore>:: When running the command with `-u` and `-m` options, the @@ -110,13 +115,21 @@ OPTIONS directories the index file and index output file are located in. +--no-sparse-checkout:: + Disable sparse checkout support even if `core.sparseCheckout` + is true. + +--empty:: + Instead of reading tree object(s) into the index, just empty + it. + <tree-ish#>:: The id of the tree object(s) to be read/merged. Merging ------- -If `-m` is specified, 'git-read-tree' can perform 3 kinds of +If `-m` is specified, 'git read-tree' can perform 3 kinds of merge, a single tree merge if only 1 tree is given, a fast-forward merge with 2 trees, or a 3-way merge if 3 trees are provided. @@ -124,18 +137,18 @@ provided. Single Tree Merge ~~~~~~~~~~~~~~~~~ -If only 1 tree is specified, 'git-read-tree' operates as if the user did not +If only 1 tree is specified, 'git read-tree' operates as if the user did not specify `-m`, except that if the original index has an entry for a -given pathname, and the contents of the path matches with the tree +given pathname, and the contents of the path match with the tree being read, the stat info from the index is used. (In other words, the index's stat()s take precedence over the merged tree's). That means that if you do a `git read-tree -m <newtree>` followed by a -`git checkout-index -f -u -a`, the 'git-checkout-index' only checks out +`git checkout-index -f -u -a`, the 'git checkout-index' only checks out the stuff that really changed. -This is used to avoid unnecessary false hits when 'git-diff-files' is -run after 'git-read-tree'. +This is used to avoid unnecessary false hits when 'git diff-files' is +run after 'git read-tree'. Two Tree Merge @@ -144,46 +157,48 @@ Two Tree Merge Typically, this is invoked as `git read-tree -m $H $M`, where $H is the head commit of the current repository, and $M is the head of a foreign tree, which is simply ahead of $H (i.e. we are in a -fast forward situation). +fast-forward situation). -When two trees are specified, the user is telling 'git-read-tree' +When two trees are specified, the user is telling 'git read-tree' the following: 1. The current index and work tree is derived from $H, but - the user may have local changes in them since $H; + the user may have local changes in them since $H. 2. The user wants to fast-forward to $M. In this case, the `git read-tree -m $H $M` command makes sure that no local change is lost as the result of this "merge". -Here are the "carry forward" rules: +Here are the "carry forward" rules, where "I" denotes the index, +"clean" means that index and work tree coincide, and "exists"/"nothing" +refer to the presence of a path in the specified commit: - I (index) H M Result + I H M Result ------------------------------------------------------- - 0 nothing nothing nothing (does not happen) - 1 nothing nothing exists use M - 2 nothing exists nothing remove path from index - 3 nothing exists exists, use M if "initial checkout" + 0 nothing nothing nothing (does not happen) + 1 nothing nothing exists use M + 2 nothing exists nothing remove path from index + 3 nothing exists exists, use M if "initial checkout", H == M keep index otherwise - exists fail + exists, fail H != M clean I==H I==M ------------------ - 4 yes N/A N/A nothing nothing keep index - 5 no N/A N/A nothing nothing keep index + 4 yes N/A N/A nothing nothing keep index + 5 no N/A N/A nothing nothing keep index - 6 yes N/A yes nothing exists keep index - 7 no N/A yes nothing exists keep index - 8 yes N/A no nothing exists fail - 9 no N/A no nothing exists fail + 6 yes N/A yes nothing exists keep index + 7 no N/A yes nothing exists keep index + 8 yes N/A no nothing exists fail + 9 no N/A no nothing exists fail 10 yes yes N/A exists nothing remove path from index 11 no yes N/A exists nothing fail 12 yes no N/A exists nothing fail 13 no no N/A exists nothing fail - clean (H=M) + clean (H==M) ------ 14 yes exists exists keep index 15 no exists exists keep index @@ -198,26 +213,26 @@ Here are the "carry forward" rules: 21 no yes no exists exists fail In all "keep index" cases, the index entry stays as in the -original index file. If the entry were not up to date, -'git-read-tree' keeps the copy in the work tree intact when +original index file. If the entry is not up to date, +'git read-tree' keeps the copy in the work tree intact when operating under the -u flag. -When this form of 'git-read-tree' returns successfully, you can -see what "local changes" you made are carried forward by running +When this form of 'git read-tree' returns successfully, you can +see which of the "local changes" that you made were carried forward by running `git diff-index --cached $M`. Note that this does not -necessarily match `git diff-index --cached $H` would have +necessarily match what `git diff-index --cached $H` would have produced before such a two tree merge. This is because of cases 18 and 19 --- if you already had the changes in $M (e.g. maybe you picked it up via e-mail in a patch form), `git diff-index --cached $H` would have told you about the change before this merge, but it would not show in `git diff-index --cached $M` -output after two-tree merge. +output after the two-tree merge. -Case #3 is slightly tricky and needs explanation. The result from this +Case 3 is slightly tricky and needs explanation. The result from this rule logically should be to remove the path if the user staged the removal of the path and then switching to a new branch. That however will prevent the initial checkout from happening, so the rule is modified to use M (new -tree) only when the contents of the index is empty. Otherwise the removal +tree) only when the content of the index is empty. Otherwise the removal of the path is kept as long as $H and $M are the same. 3-Way Merge @@ -225,7 +240,7 @@ of the path is kept as long as $H and $M are the same. Each "index" entry has two bits worth of "stage" state. stage 0 is the normal one, and is the only one you'd see in any kind of normal use. -However, when you do 'git-read-tree' with three trees, the "stage" +However, when you do 'git read-tree' with three trees, the "stage" starts out at 1. This means that you can do @@ -241,7 +256,7 @@ branch into the current branch, we use the common ancestor tree as <tree1>, the current branch head as <tree2>, and the other branch head as <tree3>. -Furthermore, 'git-read-tree' has special-case logic that says: if you see +Furthermore, 'git read-tree' has special-case logic that says: if you see a file that matches in all respects in the following states, it "collapses" back to "stage0": @@ -257,7 +272,7 @@ a file that matches in all respects in the following states, it - stage 1 and stage 3 are the same and stage 2 is different take stage 2 (we did something while they did nothing) -The 'git-write-tree' command refuses to write a nonsensical tree, and it +The 'git write-tree' command refuses to write a nonsensical tree, and it will complain about unmerged entries if it sees a single entry that is not stage 0. @@ -268,12 +283,12 @@ merge. The different stages represent the "result tree" (stage 0, aka you are trying to merge (stage 2 and 3 respectively). The order of stages 1, 2 and 3 (hence the order of three -<tree-ish> command line arguments) are significant when you +<tree-ish> command-line arguments) are significant when you start a 3-way merge with an index file that is already populated. Here is an outline of how the algorithm works: - if a file exists in identical format in all three trees, it will - automatically collapse to "merged" state by 'git-read-tree'. + automatically collapse to "merged" state by 'git read-tree'. - a file that has _any_ difference what-so-ever in the three trees will stay as separate entries in the index. It's up to "porcelain @@ -297,8 +312,8 @@ populated. Here is an outline of how the algorithm works: matching "stage1" entry if it exists too. .. all the normal trivial rules .. -You would normally use 'git-merge-index' with supplied -'git-merge-one-file' to do this last step. The script updates +You would normally use 'git merge-index' with supplied +'git merge-one-file' to do this last step. The script updates the files in the working tree as it merges each path and at the end of a successful merge. @@ -320,13 +335,13 @@ $ JC=`git rev-parse --verify "HEAD^0"` $ git checkout-index -f -u -a $JC ---------------- -You do random edits, without running 'git-update-index'. And then +You do random edits, without running 'git update-index'. And then you notice that the tip of your "upstream" tree has advanced since you pulled from him: ---------------- $ git fetch git://.... linus -$ LT=`cat .git/FETCH_HEAD` +$ LT=`git rev-parse FETCH_HEAD` ---------------- Your work tree is still based on your HEAD ($JC), but you have @@ -346,34 +361,71 @@ your work-in-progress changes, and your work tree would be updated to the result of the merge. However, if you have local changes in the working tree that -would be overwritten by this merge, 'git-read-tree' will refuse +would be overwritten by this merge, 'git read-tree' will refuse to run to prevent your changes from being lost. In other words, there is no need to worry about what exists only in the working tree. When you have local changes in a part of the project that is not involved in the merge, your changes do not interfere with the merge, and are kept intact. When they -*do* interfere, the merge does not even start ('git-read-tree' +*do* interfere, the merge does not even start ('git read-tree' complains loudly and fails without modifying anything). In such a case, you can simply continue doing what you were in the middle of doing, and when your working tree is ready (i.e. you have finished your work-in-progress), attempt the merge again. +Sparse checkout +--------------- + +"Sparse checkout" allows populating the working directory sparsely. +It uses the skip-worktree bit (see linkgit:git-update-index[1]) to tell +Git whether a file in the working directory is worth looking at. + +'git read-tree' and other merge-based commands ('git merge', 'git +checkout'...) can help maintaining the skip-worktree bitmap and working +directory update. `$GIT_DIR/info/sparse-checkout` is used to +define the skip-worktree reference bitmap. When 'git read-tree' needs +to update the working directory, it resets the skip-worktree bit in the index +based on this file, which uses the same syntax as .gitignore files. +If an entry matches a pattern in this file, skip-worktree will not be +set on that entry. Otherwise, skip-worktree will be set. + +Then it compares the new skip-worktree value with the previous one. If +skip-worktree turns from set to unset, it will add the corresponding +file back. If it turns from unset to set, that file will be removed. + +While `$GIT_DIR/info/sparse-checkout` is usually used to specify what +files are in, you can also specify what files are _not_ in, using +negate patterns. For example, to remove the file `unwanted`: + +---------------- +/* +!unwanted +---------------- + +Another tricky thing is fully repopulating the working directory when you +no longer want sparse checkout. You cannot just disable "sparse +checkout" because skip-worktree bits are still in the index and your working +directory is still sparsely populated. You should re-populate the working +directory with the `$GIT_DIR/info/sparse-checkout` file content as +follows: + +---------------- +/* +---------------- + +Then you can disable sparse checkout. Sparse checkout support in 'git +read-tree' and similar commands is disabled by default. You need to +turn `core.sparseCheckout` on in order to have sparse checkout +support. + + SEE ALSO -------- linkgit:git-write-tree[1]; linkgit:git-ls-files[1]; linkgit:gitignore[5] - -Author ------- -Written by Linus Torvalds <torvalds@osdl.org> - -Documentation --------------- -Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. - GIT --- Part of the linkgit:git[1] suite |