t7800 test failure

From: Armin Kunaschik <megabreit@googlemail.com>
Date: May 24, 2016, 15:53 UTC
Message-ID: <CALR6jEiJwx14zAyond9ggz29Q64Fz84URtjr8zaddjnrdY7TjA@mail.gmail.com>

t7800 fails on systems where readlink (GNUism?) is not available. An easy workaround for the very basic readlink usage of this test would be to use a shell function like this:

---

diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index ff7a9e9..be3d19f 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -420,6 +420,7 @@ run_dir_diff_test 'difftool --dir-diff when
worktree file is missing' '
 '

 write_script .git/CHECK_SYMLINKS <<\EOF
+readlink() { ls -ld "$1" | sed 's/.* -> //'; }
 for f in file file2 sub/sub
 do
        echo "$f"