Implement 'git stash save --patch'

This adds a hunk-based mode to git-stash.  You can select hunks from
the difference between HEAD and worktree, and git-stash will build a
stash that reflects these changes.  The index state of the stash is
the same as your current index, and we also let --patch imply
--keep-index.

Note that because the selected hunks are rolled back from the worktree
but not the index, the resulting state may appear somewhat confusing
if you had also staged these changes.  This is not entirely
satisfactory, but due to the way stashes are applied, other solutions
would require a change to the stash format.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/t/t3904-stash-patch.sh b/t/t3904-stash-patch.sh
new file mode 100755
index 0000000..f37e3bc
--- /dev/null
+++ b/t/t3904-stash-patch.sh
@@ -0,0 +1,55 @@
+#!/bin/sh
+
+test_description='git checkout --patch'
+. ./lib-patch-mode.sh
+
+test_expect_success 'setup' '
+	mkdir dir &&
+	echo parent > dir/foo &&
+	echo dummy > bar &&
+	git add bar dir/foo &&
+	git commit -m initial &&
+	test_tick &&
+	test_commit second dir/foo head &&
+	echo index > dir/foo &&
+	git add dir/foo &&
+	set_and_save_state bar bar_work bar_index &&
+	save_head
+'
+
+# note: bar sorts before dir, so the first 'n' is always to skip 'bar'
+
+test_expect_success 'saying "n" does nothing' '
+	set_state dir/foo work index
+	(echo n; echo n) | test_must_fail git stash save -p &&
+	verify_state dir/foo work index &&
+	verify_saved_state bar
+'
+
+test_expect_success 'git stash -p' '
+	(echo n; echo y) | git stash save -p &&
+	verify_state dir/foo head index &&
+	verify_saved_state bar &&
+	git reset --hard &&
+	git stash apply &&
+	verify_state dir/foo work head &&
+	verify_state bar dummy dummy
+'
+
+test_expect_success 'git stash -p --no-keep-index' '
+	set_state dir/foo work index &&
+	set_state bar bar_work bar_index &&
+	(echo n; echo y) | git stash save -p --no-keep-index &&
+	verify_state dir/foo head head &&
+	verify_state bar bar_work dummy &&
+	git reset --hard &&
+	git stash apply --index &&
+	verify_state dir/foo work index &&
+	verify_state bar dummy bar_index
+'
+
+test_expect_success 'none of this moved HEAD' '
+	verify_saved_head
+'
+
+test_done