stash: fix accidental apply of non-existent stashes

Once upon a time, "git rev-parse ref@{9999999}" did not
generate an error. Therefore when we got an invalid stash
reference in "stash apply", we could end up not noticing
until quite late.  Commit b0f0ecd (detached-stash: work
around git rev-parse failure to detect bad log refs,
2010-08-21) handled this by checking for the "Log for stash
has only %d entries" warning on stderr when we validated the
ref.

A few days later, e6eedc3 (rev-parse: exit with non-zero
status if ref@{n} is not valid., 2010-08-24) fixed the
original issue. That made the extra stderr test superfluous,
but also introduced a new bug. Now the early call to:

  git rev-parse --symbolic "$@"

fails, but we don't notice the exit code. Worse, its empty
output means we think the user didn't provide us a ref, and
we try to apply stash@{0}.

This patch checks the rev-parse exit code and fails early in
the revision parsing process. We can also get rid of the
stderr test; as a bonus, this means that "stash apply" can
now run under GIT_TRACE=1 properly.

Signed-off-by: Jeff King <[email protected]>
Acked-by: Jon Seymour <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

git-stash.sh

@@ -264,7 +264,7 @@ parse_flags_and_rev()
 	b_tree=
 	i_tree=
 
-	REV=$(git rev-parse --no-flags --symbolic "$@" 2>/dev/null)
+	REV=$(git rev-parse --no-flags --symbolic "$@") || exit 1
 
 	FLAGS=
 	for opt
@@ -310,16 +310,6 @@ parse_flags_and_rev()
 	IS_STASH_LIKE=t &&
 	test "$ref_stash" = "$(git rev-parse --symbolic-full-name "${REV%@*}")" &&
 	IS_STASH_REF=t
-
-	if test "${REV}" != "${REV%{*\}}"
-	then
-		# maintainers: it would be better if git rev-parse indicated
-		# this condition with a non-zero status code but as of 1.7.2.1 it
-		# it did not. So, we use non-empty stderr output as a proxy for the
-		# condition of interest.
-		test -z "$(git rev-parse "$REV" 2>&1 >/dev/null)" || die "$REV does not exist in the stash log"
-	fi
-
 }
 
 is_stash_like()

t/t3903-stash.sh

@@ -37,6 +37,12 @@ test_expect_success 'parents of stash' '
 	test_cmp output expect
 '
 
+test_expect_success 'applying bogus stash does nothing' '
+	test_must_fail git stash apply stash@{1} &&
+	echo 1 >expect &&
+	test_cmp expect file
+'
+
 test_expect_success 'apply needs clean working directory' '
 	echo 4 > other-file &&
 	git add other-file &&