Merge branch 'jk/stash-disable-renames-internally' into maint

When diff.renames configuration is on (and with Git 2.9 and later,
it is enabled by default, which made it worse), "git stash"
misbehaved if a file is removed and another file with a very
similar content is added.

* jk/stash-disable-renames-internally:
  stash: prefer plumbing over git-diff

git-stash.sh

@@ -115,7 +115,7 @@ create_stash () {
 			git read-tree --index-output="$TMPindex" -m $i_tree &&
 			GIT_INDEX_FILE="$TMPindex" &&
 			export GIT_INDEX_FILE &&
-			git diff --name-only -z HEAD -- >"$TMP-stagenames" &&
+			git diff-index --name-only -z HEAD -- >"$TMP-stagenames" &&
 			git update-index -z --add --remove --stdin <"$TMP-stagenames" &&
 			git write-tree &&
 			rm -f "$TMPindex"

t/t3903-stash.sh

@@ -766,4 +766,13 @@ test_expect_success 'stash list --cc shows combined diff' '
 	test_cmp expect actual
 '
 
+test_expect_success 'stash is not confused by partial renames' '
+	mv file renamed &&
+	git add renamed &&
+	git stash &&
+	git stash apply &&
+	test_path_is_file renamed &&
+	test_path_is_missing file
+'
+
 test_done