checkout -p: handle new files correctly

The original patch selection code was written for `git add -p`, and the
fundamental unit on which it works is a hunk.

We hacked around that to handle deletions back in 24ab81ae4d
(add-interactive: handle deletion of empty files, 2009-10-27). But `git
add -p` would never see a new file, since we only consider the set of
tracked files in the index.

However, since the same machinery was used for `git checkout -p` &
friends, we can see new files.

Handle this case specifically, adding a new prompt for it that is
modeled after the `deleted file` case.

This also fixes the problem where added _empty_ files could not be
staged via `git checkout -p`.

Reported-by: Merlin Büge <toni@bluenox07.de>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index ac43f835a5..7bc0c3fe6e 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh
@@ -403,6 +403,25 @@ test_expect_success 'deleting an empty file' '
 	diff_cmp expected diff
 '
 
+test_expect_success 'adding an empty file' '
+	git init added &&
+	(
+		cd added &&
+		test_commit initial &&
+		>empty &&
+		git add empty &&
+		test_tick &&
+		git commit -m empty &&
+		git tag added-file &&
+		git reset --hard HEAD^ &&
+		test_path_is_missing empty &&
+
+		echo y | git checkout -p added-file -- >actual &&
+		test_path_is_file empty &&
+		test_i18ngrep "Apply addition to index and worktree" actual
+	)
+'
+
 test_expect_success 'split hunk setup' '
 	git reset --hard &&
 	test_write_lines 10 20 30 40 50 60 >test &&