stash: require a clean index to apply

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> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Apr 22, 2015 at 15:31 UTC ed178ef13a26136d86ff4e33bb7b1afb5033f908
2 files changed +9
git-stash.sh
+2
@@ -442,6 +442,8 @@ apply_stash () {
442 assert_stash_like "$@"
443
444 git update-index -q --refresh || die "$(gettext "unable to refresh index")"
445 + git diff-index --cached --quiet --ignore-submodules HEAD -- ||
446 + die "$(gettext "Cannot apply stash: Your index contains uncommitted changes.")"
447
448 # current index state
449 c_tree=$(git write-tree) ||
t/t3903-stash.sh
+7
@@ -45,6 +45,13 @@ test_expect_success 'applying bogus stash does nothing' '
45 test_cmp expect file
46 '
47
48 +test_expect_success 'apply requires a clean index' '
49 + test_when_finished "git reset --hard" &&
50 + echo changed >other-file &&
51 + git add other-file &&
52 + test_must_fail git stash apply
53 +'
54 +
55 test_expect_success 'apply does not need clean working directory' '
56 echo 4 >other-file &&
57 git stash apply &&