[PATCH v2] difftool --dir-diff: always use identical working tree file

[Kenichi Saita <nitoyon@gmail.com>]

When deciding whether or not we should link a working tree file into
the temporary right-hand directory for a directory diff, we
currently behave differently in the --symlink and --no-symlink
cases.  If using symlinks any identical files are linked across but
with --no-symlink only files that contain unstaged changes are
copied back into the working tree.

Change this so that identical files are copied back as well.  This
is beneficial because it widens the set of circumstances in which we
copy changes made by the user back into the working tree.

Signed-off-by: Kenichi Saita <nitoyon@gmail.com>
---
 git-difftool.perl   |    9 ++-------
 t/t7800-difftool.sh |   19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/git-difftool.perl b/git-difftool.perl
index 8a75205..e57d3d1 100755
--- a/git-difftool.perl
+++ b/git-difftool.perl
@@ -85,13 +85,9 @@ sub exit_cleanup
 
 sub use_wt_file
 {
-	my ($repo, $workdir, $file, $sha1, $symlinks) = @_;
+	my ($repo, $workdir, $file, $sha1) = @_;
 	my $null_sha1 = '0' x 40;
 
-	if ($sha1 ne $null_sha1 and not $symlinks) {
-		return 0;
-	}
-
 	if (! -e "$workdir/$file") {
 		# If the file doesn't exist in the working tree, we cannot
 		# use it.
@@ -213,8 +209,7 @@ EOF
 
 		if ($rmode ne $null_mode) {
 			my ($use, $wt_sha1) = use_wt_file($repo, $workdir,
-							  $dst_path, $rsha1,
-							  $symlinks);
+							  $dst_path, $rsha1);
 			if ($use) {
 				push @working_tree, $dst_path;
 				$wtindex .= "$rmode $wt_sha1\t$dst_path\0";
diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index d46f041..2418528 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -385,6 +385,25 @@ test_expect_success PERL,SYMLINKS 'difftool --dir-diff --symlink without unstage
 	test_cmp actual expect
 '
 
+write_script modify-right-file <<\EOF
+echo "new content" >"$2/file"
+EOF
+
+run_dir_diff_test 'difftool --dir-diff syncs worktree with unstaged change' '
+	test_when_finished git reset --hard &&
+	echo "orig content" >file &&
+	git difftool -d $symlinks --extcmd "$(pwd)/modify-right-file" branch &&
+	echo "new content" >expect &&
+	test_cmp expect file
+'
+
+run_dir_diff_test 'difftool --dir-diff syncs worktree without unstaged change' '
+	test_when_finished git reset --hard &&
+	git difftool -d $symlinks --extcmd "$(pwd)/modify-right-file" branch &&
+	echo "new content" >expect &&
+	test_cmp expect file
+'
+
 write_script modify-file <<\EOF
 echo "new content" >file
 EOF
-- 
1.7.1