From bba067d2faf047597bc76f885fb0cf87894b5ed1 Mon Sep 17 00:00:00 2001
From: Thomas Gummerer <t.gummerer@gmail.com>
Date: Sat, 6 Jan 2018 00:24:20 +0000
Subject: [PATCH] stash: don't delete untracked files that match pathspec

Currently when 'git stash push -- <pathspec>' is used, untracked files
that match the pathspec will be deleted, even though they do not end up
in a stash anywhere.

This is because the original commit introducing the pathspec feature in
git stash push (df6bba0937 ("stash: teach 'push' (and 'create_stash') to
honor pathspec", 2017-02-28)) used the sequence of 'git reset <pathspec>
&& git ls-files --modified <pathspec> | git checkout-index && git clean
<pathspec>'.

The intention was to emulate what 'git reset --hard -- <pathspec>' would
do.  The call to 'git clean' was supposed to clean up the files that
were unstaged by 'git reset'.  This would work fine if the pathspec
doesn't match any files that were untracked before 'git stash push --
<pathspec>'.  However if <pathspec> matches a file that was untracked
before invoking the 'stash' command, all untracked files matching the
pathspec would inadvertently be deleted as well, even though they
wouldn't end up in the stash, and are therefore lost.

This behaviour was never what was intended, only blobs that also end up
in the stash should be reset to their state in HEAD, previously
untracked files should be left alone.

To achieve this, first match what's in the index and what's in the
working tree by adding all changes to the index, ask diff-index what
changed between HEAD and the current index, and then apply that patch in
reverse to get rid of the changes, which includes removal of added
files and resurrection of removed files.

Reported-by: Reid Price <reid.price@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 git-stash.sh     |  5 ++---
 t/t3903-stash.sh | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/git-stash.sh b/git-stash.sh
index 8b2ce9afda..b48b164748 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -315,10 +315,9 @@ push_stash () {
 
 		if test $# != 0
 		then
-			git reset -q -- "$@"
-			git ls-files -z --modified -- "$@" |
+			git add -u -- "$@" |
 			git checkout-index -z --force --stdin
-			git clean --force -q -d -- "$@"
+			git diff-index -p --cached --binary HEAD -- "$@" | git apply --index -R
 		else
 			git reset --hard -q
 		fi
diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
index 3b1ac1971a..1cd85e70e9 100755
--- a/t/t3903-stash.sh
+++ b/t/t3903-stash.sh
@@ -971,4 +971,36 @@ test_expect_success 'stash -k -- <pathspec> leaves unstaged files intact' '
 	test foo,bar = $(cat foo),$(cat bar)
 '
 
+test_expect_success 'stash -- <subdir> leaves untracked files in subdir intact' '
+	git reset &&
+	>subdir/untracked &&
+	>subdir/tracked1 &&
+	>subdir/tracked2 &&
+	git add subdir/tracked* &&
+	git stash -- subdir/ &&
+	test_path_is_missing subdir/tracked1 &&
+	test_path_is_missing subdir/tracked2 &&
+	test_path_is_file subdir/untracked &&
+	git stash pop &&
+	test_path_is_file subdir/tracked1 &&
+	test_path_is_file subdir/tracked2 &&
+	test_path_is_file subdir/untracked
+'
+
+test_expect_success 'stash -- <subdir> works with binary files' '
+	git reset &&
+	>subdir/untracked &&
+	>subdir/tracked &&
+	cp "$TEST_DIRECTORY"/test-binary-1.png subdir/tracked-binary &&
+	git add subdir/tracked* &&
+	git stash -- subdir/ &&
+	test_path_is_missing subdir/tracked &&
+	test_path_is_missing subdir/tracked-binary &&
+	test_path_is_file subdir/untracked &&
+	git stash pop &&
+	test_path_is_file subdir/tracked &&
+	test_path_is_file subdir/tracked-binary &&
+	test_path_is_file subdir/untracked
+'
+
 test_done
-- 
2.11.4.GIT