From a0f83e777660dbf7d9526c05d94fc920e459aed9 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Fri, 6 Jan 2023 06:03:57 -0500 Subject: diff: use filespec path to set up tempfiles for ext-diff 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 Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- diff.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'diff.c') diff --git a/diff.c b/diff.c index 1054a4b732..c78ea27033 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); -- cgit v1.2.3