[PATCH 1/3] diff: use filespec path to set up tempfiles for ext-diff
- From
Jeff King <peff@peff.net>
- Date
- Jan 6, 2023, 11:03 UTC
- Message-ID
- <Y7gAHenwmIo4gXTb@coredump.intra.peff.net>
- In-Reply-To
- <Y7f/YiVu1TgbucDI@coredump.intra.peff.net>
When we're going to run an external diff, we have to make the contents of the pre- and post-images available either by dumping them to a tempfile, or by pointing at a valid file in the worktree. The logic of this is all handled by prepare_temp_file(), and we just pass in the filename and the diff_filespec.
But there's a gotcha here. The "filename" we have is a logical filename and not necessarily a path on disk or in the repository. This matters in at least one case: when using "--relative", we may have a name like "foo", even though the file content is found at "subdir/foo". As a result, we look for the wrong path, fail to find "foo", and claim that the file has been deleted (passing "/dev/null" to the external diff, rather than the correct worktree path).
We can fix this by passing the pathname from the diff_filespec, which should always be a full repository path (and that's what we want even if reusing a worktree file, since we're always operating from the top-level of the working tree).
The breakage seems to go all the way back to cd676a5136 (diff --relative: output paths as relative to the current subdirectory, 2008-02-12). As far as I can tell, before then "name" would always have been the same as the filespec's "path".
There are two related cases I looked at that aren't buggy:
1. the only other caller of prepare_temp_file() is run_textconv(). But
it always passes the filespec's path field, so it's OK. 2. I wondered if file renames/copies might cause similar confusion.
But they don't, because run_external_diff() receives two names in
that case: "name" and "other", which correspond to the two sides of
the diff. And we did correctly pass "other" when handling the
post-image side. Barring the use of "--relative", that would always
match "two->path", the path of the second filespec (and the rename
destination).So the only bug is just the interaction with external diff drivers and --relative.
Reported-by: Carl Baldwin <carl@ecbaldwin.net> Signed-off-by: Jeff King <peff@peff.net> --- diff.c | 2 +- t/t4045-diff-relative.sh | 29 +++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/diff.c b/diff.c index 9b14543e6e..59039773a1 100644 --- a/diff.c +++ b/diff.c @@ -4281,7 +4281,7 @@ static void add_external_diff_name(struct repository *r, const char *name, struct diff_filespec *df) { - struct diff_tempfile *temp = prepare_temp_file(r, name, df); + struct diff_tempfile *temp = prepare_temp_file(r, df->path, df); strvec_push(argv, temp->name); strvec_push(argv, temp->hex); strvec_push(argv, temp->mode); diff --git a/t/t4045-diff-relative.sh b/t/t4045-diff-relative.sh index 198dfc9190..9b46c4c1be 100755 --- a/t/t4045-diff-relative.sh +++ b/t/t4045-diff-relative.sh @@ -164,6 +164,35 @@ check_diff_relative_option subdir file2 true --no-relative --relative check_diff_relative_option . file2 false --no-relative --relative=subdir check_diff_relative_option . file2 true --no-relative --relative=subdir +test_expect_success 'external diff with --relative' ' + test_when_finished "git reset --hard" && + echo changed >file1 && + echo changed >subdir/file2 && + + write_script mydiff <<-\EOF && + # hacky pretend diff; the goal here is just to make sure we got + # passed sensible input that we _could_ diff, without relying on + # the specific output of a system diff tool. + echo "diff a/$1 b/$1" && + echo "--- a/$1" && + echo "+++ b/$1" && + echo "@@ -1 +0,0 @@" && + sed "s/^/-/" "$2" && + sed "s/^/+/" "$5" + EOF + + cat >expect <<-\EOF && + diff a/file2 b/file2 + --- a/file2 + +++ b/file2 + @@ -1 +0,0 @@ + -other content + +changed + EOF + GIT_EXTERNAL_DIFF=./mydiff git diff --relative=subdir >actual && + test_cmp expect actual +' + test_expect_success 'setup diff --relative unmerged' ' test_commit zero file0 && test_commit base subdir/file0 &&
-- 2.39.0.463.g3774f23bc9