git: Only reset Git index if non-empty #3748
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Out of curiosity, do you see any performance improvement in the gix version?
https://github.com/yuja/jj/tree/push-vpsmwmxpokyx
I haven't pushed the gix version because it adds more code, needs cleanup, and lacks testing. If it's faster than the current libgit2 impl, maybe I should restart the rewrite.
In chromium/src.git, this gives an approximate ~0.83s speedup for commands if the Git index is empty, and a ~0.14s slowdown if the Git index is non-empty. As most users using jj will likely be using jj to write to a colocated repo - and therefore avoid modifying the Git index - this should be a general speedup for most colocated checkouts.
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@yuja The gix implementation is noticeably faster! With this PR, it takes around ~3.0s to do a However, it does cause weird things with the state of the git repo - a I also noticed that my p10k git prompt shows a very large number of modified files when it is in this weird state, which is fixed after a (slow) |
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The gix implementation is noticeably faster! With this PR, it takes around ~3.0s to do a
jj abandonwhen@is empty. With your gix implementation, it takes ~2.4s.However, it does cause weird things with the state of the git repo - a
git statusafterwards causes a long "Refresh index" operation (~80s, then ~36s, then ~36s) to occur,
Perhaps, that's because my version doesn't preserve mtime/ctime stored in the index. I haven't noticed it because I don't use git for working-copy management.
Thanks for testing. I think this PR is good workaround. We'll need some diffing (to copy back mtime/ctime) anyway if we switch to gix.
This accounts for commit message-only changes which do not change the tree ID, as well as checkouts between commits with identical tree contents. See martinvonz#3748 for previous work on avoiding resetting HEAD when the *commits* are identical.
This accounts for commit message-only changes which do not change the tree ID, as well as checkouts between commits with identical tree contents. See martinvonz#3748 for previous work on avoiding resetting HEAD when the *commits* are identical.
This accounts for commit message-only changes which do not change the tree ID, as well as checkouts between commits with identical tree contents. See martinvonz#3748 for previous work on avoiding resetting HEAD when the *commits* are identical.
This accounts for commit message-only changes which do not change the tree ID, as well as checkouts between commits with identical tree contents. See martinvonz#3748 for previous work on avoiding resetting HEAD when the *commits* are identical.
This accounts for commit message-only changes which do not change the tree ID, as well as checkouts between commits with identical tree contents. See #3748 for previous work on avoiding resetting HEAD when the *commits* are identical.
In chromium/src.git, this gives an approximate ~0.83s speedup for commands if the Git index is empty, and a ~0.14s slowdown if the Git index is non-empty.
As most users using jj will likely be using jj to write to a colocated repo - and therefore avoid modifying the Git index - this should be a general speedup for most colocated checkouts.
Checklist
If applicable:
CHANGELOG.md