[PATCH 3/3] stash: require a clean index to apply

From: Jeff King <peff@peff.net>
Date: Apr 22, 2015, 19:31 UTC
Message-ID: <20150422193101.GC27945@peff.net>
In-Reply-To: <20150422192948.GA27656@peff.net>

If you have staged contents in your index and run "stash apply", we may hit a conflict and put new entries into the index. Recovering to your original state is difficult at that point, because tools like "git reset --keep" will blow away anything staged. We can make this safer by refusing to apply when there are staged changes.

It's possible we could provide better tooling here, as "git stash apply" should be writing only conflicts to the index (so we know that any stage-0 entries are potentially precious). But it is the odd duck; most "mergy" commands will update the index for cleanly merged entries, and it is not worth updating our tooling to support this use case which is unlikely to be of interest (besides which, we would still need to block a dirty index for "stash apply --index", since that case _would_ be ambiguous).

Signed-off-by: Jeff King <peff@peff.net>
---
 git-stash.sh     | 2 ++
 t/t3903-stash.sh | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/git-stash.sh b/git-stash.sh
index d4cf818..cc28368 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -442,6 +442,8 @@ apply_stash () {
 	assert_stash_like "$@"
 
 	git update-index -q --refresh || die "$(gettext "unable to refresh index")"
+	git diff-index --cached --quiet --ignore-submodules HEAD -- ||
+		die "$(gettext "Cannot apply stash: Your index contains uncommitted changes.")"
 
 	# current index state
 	c_tree=$(git write-tree) ||
diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
index f179c93..0746eee 100755
--- a/t/t3903-stash.sh
+++ b/t/t3903-stash.sh
@@ -45,6 +45,13 @@ test_expect_success 'applying bogus stash does nothing' '
 	test_cmp expect file
 '
 
+test_expect_success 'apply requires a clean index' '
+	test_when_finished "git reset --hard" &&
+	echo changed >other-file &&
+	git add other-file &&
+	test_must_fail git stash apply
+'
+
 test_expect_success 'apply does not need clean working directory' '
 	echo 4 >other-file &&
 	git stash apply &&

-- 
2.4.0.rc2.498.g02440db