问题
I have local changes to a file that I don\'t want to commit to my repository. It is a configuration file for building the application on a server, but I want to build locally with different settings. Naturally, the file always shows up when i do \'git status\' as something to be staged. I would like to hide this particular change and not commit it. I won\'t make any other changes to the file.
After some digging around, I see 2 options: \'assume-unchanged\' and \'skip-worktree\'. A previous question here talks about them but doesn\'t really explain their differences. My question is this: how are the two commands different? Why would someone use one or the other?
回答1:
You want skip-worktree
.
assume-unchanged
is designed for cases where it is expensive to check whether a group of files have been modified; when you set the bit, git
(of course) assumes the files corresponding to that portion of the index have not been modified in the working copy. So it avoids a mess of stat
calls. This bit is lost whenever the file's entry in the index changes (so, when the file is changed upstream).
skip-worktree
is more than that: even where git
knows that the file has been modified (or needs to be modified by a reset --hard
or the like), it will pretend it has not been, using the version from the index instead. This persists until the index is discarded.
There is a good summary of the ramifications of this difference and the typical use cases here: http://fallengamer.livejournal.com/93321.html .
From that article:
--assume-unchanged
assumes that a developer shouldn’t change a file. This flag is meant for improving performance for not-changing folders like SDKs.--skip-worktree
is useful when you instruct git not to touch a specific file ever because developers should change it. For example, if the main repository upstream hosts some production-ready configuration files and you don’t want to accidentally commit changes to those files,--skip-worktree
is exactly what you want.
回答2:
Note: fallengamer did some tests in 2011 (so they may be outdated), and here are his findings:
Operations
- File is changed both in local repository and upstream
git pull
:
Git preserves local changes anyway.
Thus you wouldn’t accidentally lose any data that you marked with any of the flags.- File with
assume-unchanged
flag: Git wouldn’t overwrite local file. Instead it would output conflicts and advices how to resolve them - File with
skip-worktree
flag: Git wouldn’t overwrite local file. Instead it would output conflicts and advices how to resolve them
- File with
- File is changed both in local repository and upstream, trying to pull anyway
git stash
git pull
Usingskip-worktree
results in some extra manual work but at least you wouldn’t lose any data if you had any local changes.- File with
assume-unchanged
flag: Discards all local changes without any possibility to restore them. The effect is like ‘git reset --hard
’. ‘git pull
’ call will succeed - File with
skip-worktree
flag: Stash wouldn’t work onskip-worktree
files. ‘git pull
’ will fail with the same error as above. Developer is forced to manually resetskip-worktree
flag to be able to stash and complete the failingpull
.
- File with
- No local changes, upstream file changed
git pull
Both flags wouldn’t prevent you from getting upstream changes. Git detects that you brokeassume-unchanged
promise and choses to reflect the reality by resetting the flag.- File with
assume-unchanged
flag: Content is updated, flag is lost.
‘git ls-files -v
’ would show that flag is modified toH
(fromh
). - File with
skip-worktree
flag: Content is updated, flag is preserved.
‘git ls-files -v
' would show the sameS
flag as before thepull
.
- File with
- With local file changed
git reset --hard
Git doesn’t touchskip-worktree
file and reflects reality (the file promised to be unchanged actually was changed) forassume-unchanged
file.- File with
assume-unchanged
flag: File content is reverted. Flag is reset toH
(fromh
). - File with
skip-worktree
flag: File content is intact. Flag remains the same.
- File with
He adds the following analysis:
It looks like
skip-worktree
is trying very hard to preserve your local data. But it doesn’t prevent you to get upstream changes if it is safe. Plus git doesn’t reset the flag onpull
.
But ignoring the ‘reset --hard
' command could become a nasty surprise for a developer.Assume-unchanged
flag could be lost on thepull
operation and the local changes inside such files doesn’t seem to be important to git.
See:
Junio's (current git maintainer) comment regarding intent of assume-unchanged,
In particular, Junio points out that changes to
assume-unchanged
files could accidentally be committed: "if Git can determine a path that is marked asassume-unchanged
has changed without incurring extra lstat(2) cost, it reserves the right to report that the path has been modified (as a result,git commit -a
is free to commit that change)."difference between assume-unchanged and skip-worktree as discussed in git mailing list upon addition of skip-worktree patch.
He concludes:
Actually neither of the flags is intuitive enough.
assume-unchanged
assumes that a developer shouldn’t change a file. If a file was changed – then that change is not important. This flag is meant for improving performance for not-changing folders like SDKs.
But if the promise is broken and a file is actually changed, git reverts the flag to reflect the reality. Probably it’s ok to have some inconsistent flags in generally not-meant-to-be-changed folders.On the other hand
skip-worktree
is useful when you instruct git not to touch a specific file ever. That is useful for an already tracked config file.
Upstream main repository hosts some production-ready config but you would like to change some settings in the config to be able to do some local testing. And you don’t want to accidentally check the changes in such file to affect the production config. In that caseskip-worktree
makes perfect scene.
来源:https://stackoverflow.com/questions/13630849/git-difference-between-assume-unchanged-and-skip-worktree