difftool: fix dir-diff when file does not exist in working tree

Commit 02c5631 (difftool --dir-diff: symlink all files matching the
working tree, 2013-03-14) does not handle the case where a file that is
being compared does not exist in the working tree.  Fix this by checking
for existence explicitly before running git-hash-object.

Reported-by: Kevin Bracey <kevin@bracey.fi>
Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-difftool.perl b/git-difftool.perl
index 6780292..8a75205 100755 (executable)
--- a/git-difftool.perl
+++ b/git-difftool.perl
@@ -92,6 +92,12 @@ sub use_wt_file
                return 0;
        }
 
+       if (! -e "$workdir/$file") {
+               # If the file doesn't exist in the working tree, we cannot
+               # use it.
+               return (0, $null_sha1);
+       }
+
        my $wt_sha1 = $repo->command_oneline('hash-object', "$workdir/$file");
        my $use = ($sha1 eq $null_sha1) || ($sha1 eq $wt_sha1);
        return ($use, $wt_sha1);

diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index a6bd99e..d46f041 100755 (executable)
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -356,6 +356,13 @@ run_dir_diff_test 'difftool --dir-diff from subdirectory' '
        )
 '
 
+run_dir_diff_test 'difftool --dir-diff when worktree file is missing' '
+       test_when_finished git reset --hard &&
+       rm file2 &&
+       git difftool --dir-diff $symlinks --extcmd ls branch master >output &&
+       grep file2 output
+'
+
 write_script .git/CHECK_SYMLINKS <<\EOF
 for f in file file2 sub/sub
 do