t3903: stop hard-coding commit sha1s

When testing the diff output of "git stash list", we look
for the stash's subject of "WIP on master: $sha1", even
though it's not relevant to the diff output. This makes the
test brittle to refactoring, as any changes to earlier tests
may impact the commit sha1.

Since we don't care about the commit subject here, we can
simply ask stash not to print it.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3903-stash.sh

@@ -695,8 +695,8 @@ test_expect_success 'setup stash with index and worktree changes' '
 '
 
 test_expect_success 'stash list implies --first-parent -m' '
-	cat >expect <<-\EOF &&
-	stash@{0}: WIP on master: b27a2bc subdir
+	cat >expect <<-EOF &&
+	stash@{0}
 
 	diff --git a/file b/file
 	index 257cc56..d26b33d 100644
@@ -706,13 +706,13 @@ test_expect_success 'stash list implies --first-parent -m' '
 	-foo
 	+working
 	EOF
-	git stash list -p >actual &&
+	git stash list --format=%gd -p >actual &&
 	test_cmp expect actual
 '
 
 test_expect_success 'stash list --cc shows combined diff' '
 	cat >expect <<-\EOF &&
-	stash@{0}: WIP on master: b27a2bc subdir
+	stash@{0}
 
 	diff --cc file
 	index 257cc56,9015a7a..d26b33d
@@ -723,7 +723,7 @@ test_expect_success 'stash list --cc shows combined diff' '
 	 -index
 	++working
 	EOF
-	git stash list -p --cc >actual &&
+	git stash list --format=%gd -p --cc >actual &&
 	test_cmp expect actual
 '