Fix regex matching for diff output parsing.

[RRethy]

Fix #8

The regex was failing for my diff output, I'm not sure the reason for the b/ in it but let me know if this breaks something I'm unaware of. The regex I'm using is the same used in the OG git jump command.

[wincent]

Thanks for the PR! I think it needs a small tweak though, noted inline, before it can be merged.

[wincent]

So here's the original Perl regexen:

	if (m{^\+\+\+ (.*)}) { $file = $1; next }
	defined($file) or next;
	if (m/^@@ .*?\+(\d+)/) { $line = $1; next }

Thoughts on the first line: this change is seems broken. Note that it only works because the upstream script invokes git diff with --no-prefix. ie. instead of producing a "standard" diff with headers that look like this:

diff --git a/aspects/dotfiles/files/.zsh/zsh-syntax-highlighting b/aspects/dotfiles/files/.zsh/zsh-syntax-highlighting
--- a/aspects/dotfiles/files/.zsh/zsh-syntax-highlighting
+++ b/aspects/dotfiles/files/.zsh/zsh-syntax-highlighting
@@ -1 +1 @@
-Subproject commit 82cf2527fc13fefee6e87f99171c1b368f0abdb9
+Subproject commit 82cf2527fc13fefee6e87f99171c1b368f0abdb9-dirty

It produces:

diff --git aspects/dotfiles/files/.zsh/zsh-syntax-highlighting aspects/dotfiles/files/.zsh/zsh-syntax-highlighting
--- aspects/dotfiles/files/.zsh/zsh-syntax-highlighting
+++ aspects/dotfiles/files/.zsh/zsh-syntax-highlighting
@@ -1 +1 @@
-Subproject commit 82cf2527fc13fefee6e87f99171c1b368f0abdb9
+Subproject commit 82cf2527fc13fefee6e87f99171c1b368f0abdb9-dirty

You'll note that vcs-jump instead invokes git diff with git -c diff.mnemonicPrefix=no diff. From man git-config:

       diff.mnemonicPrefix
           If set, git diff uses a prefix pair that is different from the standard "a/" and "b/" depending on what is being compared. When
           this configuration is in effect, reverse diff output also swaps the order of the prefixes:

Looks like they used to do a similar thing to vcs-jump but changed it in git/git@6108b04.

So that means that with this change, and depending on local config values, the jump list will be populated with entries like a/some/file.txt instead of the desired some/file.txt.

Relevant bits from man git-diff:

       --src-prefix=<prefix>
           Show the given source prefix instead of "a/".

       --dst-prefix=<prefix>
           Show the given destination prefix instead of "b/".

       --no-prefix
           Do not show any source or destination prefix.

Note also that this means that they used to jump to the post-image file-name (which I think is better, because it will land on the renamed file if rename detection is active), but now they jump to the pre-image filename.

I think this explains why it didn't work for you before but it works with out-of-the-box settings. There is likely something in you git config --list output that would account for the behavior difference.

So, I don't think we should apply this change. Instead, we should pass additional config options to force the use of prefixes.

git -c diff.noprefix=no -c diff.mnemonicPrefix=no

Thoughts on the second line: this is just turning it into a non-greedy pattern. They made the change here. I expect this is an exceedingly rare edge case and doesn't explain the problem you were having, but we should apply the change anyway.

[RRethy]

Interesting, thanks for the detailed explanation (I did have noprefix=true in my config)! I made the change and went through https://git-scm.com/docs/diff-config to make sure there are no other config options that could cause an issue.

[wincent]

Perfect. Thanks!