From: Chris Torek <redacted>

According to the documentation, "git diff" takes at most two commit-ish,
or an A..B style range, or an A...B style symmetric difference range.
The autosquash-and-exec test relied on "git diff HEAD^!", which works
fine for ordinary commits as the revision parse produces two commit-ish,
namely ^HEAD^ and HEAD.

For merge commits, however, this test makes use of an undocumented
feature: the resulting revision parse has all the parents as UNINTERESTING
followed by the HEAD commit.  This looks identical to a symmetric
diff parse, which lists the merge bases as UNINTERESTING, followed by
the A (UNINTERESTING) and B revs.  So the diff winds up treating it
as one, using the first oid (i.e., HEAD^) and the last (i.e., HEAD).
The documentation, however, says nothing about this usage.

Since diff actually just uses HEAD^ and HEAD, call for these directly
here.  That makes it possible to improve the diff code's handling of
symmetric difference arguments.

Signed-off-by: Chris Torek <redacted>
---
 t/t3430-rebase-merges.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
index a1bc3e20016..b454f400ebd 100755
--- a/t/t3430-rebase-merges.sh
+++ b/t/t3430-rebase-merges.sh

@@ -420,7 +420,7 @@ test_expect_success 'with --autosquash and --exec' '
 	git commit --fixup B B.t &&
 	write_script show.sh <<-\EOF &&
 	subject="$(git show -s --format=%s HEAD)"
-	content="$(git diff HEAD^! | tail -n 1)"
+	content="$(git diff HEAD^ HEAD | tail -n 1)"
 	echo "$subject: $content"
 	EOF
 	test_tick &&

-- 
gitgitgadget