difftool --dir-diff: symlink all files matching the working tree

Some users like to edit files in their diff tool when using "git
difftool --dir-diff --symlink" to compare against the working tree but
difftool currently only created symlinks when a file contains unstaged
changes.

Change this behaviour so that symlinks are created whenever the
right-hand side of the comparison has the same SHA1 as the file in the
working tree.

Note that textconv filters are handled in the same way as by git-diff
and if a clean filter is not the inverse of its smudge filter we already
get a null SHA1 from "diff --raw" and will symlink the file without
going through the new hash-object based check.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index eb1d3f8..db3d3d6 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -370,6 +370,28 @@ test_expect_success PERL 'difftool --dir-diff' '
 	echo "$diff" | stdin_contains file
 '
 
+write_script .git/CHECK_SYMLINKS <<\EOF
+for f in file file2 sub/sub
+do
+	echo "$f"
+	readlink "$2/$f"
+done >actual
+EOF
+
+test_expect_success PERL,SYMLINKS 'difftool --dir-diff --symlink without unstaged changes' '
+	cat >expect <<-EOF &&
+	file
+	$(pwd)/file
+	file2
+	$(pwd)/file2
+	sub/sub
+	$(pwd)/sub/sub
+	EOF
+	git difftool --dir-diff --symlink \
+		--extcmd "./.git/CHECK_SYMLINKS" branch HEAD &&
+	test_cmp actual expect
+'
+
 test_expect_success PERL 'difftool --dir-diff ignores --prompt' '
 	diff=$(git difftool --dir-diff --prompt --extcmd ls branch) &&
 	echo "$diff" | stdin_contains sub &&