[PATCH] difftool: fix argument handling in subdirs

[John Keeping <john@keeping.me.uk>]

On Mon, Jul 04, 2016 at 08:37:39PM +0200, Bernhard Kirchen wrote:
> Today I started using --dir-diff and noticed a problem when specifying a
> non-full path limiter. My diff tool is setup to be meld (*1).
> 
> OK while working directory is repo root; also OK while working directory is
> repo subfolder "actual":
> git difftool --dir-diff HEAD~1 HEAD -- actual/existing/path
> => meld opens with proper dir-diff.
> 
> NOT OK while working directory is repo subfolder "actual":
> git difftool --dir-diff HEAD~1 HEAD -- existing/path
> => nothing happens, as if using "non/such/path" as the path limiter.
> 
> Because "git diff HEAD~1 HEAD -- existing/path" while the working directory
> is the repo subfolder "actual" works, I epxected the difftool to work
> similarly. Is this a bug?

I think it is, yes.  The patch below fixes it for me and doesn't break
any existing tests, but I still don't understand why the separate
$diffrepo was needed originally, so I'm not certain this won't break
some other corner case.

-- >8 --
When in a subdirectory of a repository, path arguments should be
interpreted relative to the current directory not the root of the
working tree.

The Git::repository object passed into setup_dir_diff() is configured to
handle this correctly but we create a new Git::repository here without
setting the WorkingSubdir argument.  By simply using the existing
repository, path arguments are handled relative to the current
directory.

Signed-off-by: John Keeping <john@keeping.me.uk>
---
 git-difftool.perl | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/git-difftool.perl b/git-difftool.perl
index ebd13ba..c9d3ef8 100755
--- a/git-difftool.perl
+++ b/git-difftool.perl
@@ -115,16 +115,9 @@ sub setup_dir_diff
 {
 	my ($repo, $workdir, $symlinks) = @_;
 
-	# Run the diff; exit immediately if no diff found
-	# 'Repository' and 'WorkingCopy' must be explicitly set to insure that
-	# if $GIT_DIR and $GIT_WORK_TREE are set in ENV, they are actually used
-	# by Git->repository->command*.
 	my $repo_path = $repo->repo_path();
-	my %repo_args = (Repository => $repo_path, WorkingCopy => $workdir);
-	my $diffrepo = Git->repository(%repo_args);
-
 	my @gitargs = ('diff', '--raw', '--no-abbrev', '-z', @ARGV);
-	my $diffrtn = $diffrepo->command_oneline(@gitargs);
+	my $diffrtn = $repo->command_oneline(@gitargs);
 	exit(0) unless defined($diffrtn);
 
 	# Build index info for left and right sides of the diff
@@ -176,12 +169,12 @@ EOF
 
 		if ($lmode eq $symlink_mode) {
 			$symlink{$src_path}{left} =
-				$diffrepo->command_oneline('show', "$lsha1");
+				$repo->command_oneline('show', "$lsha1");
 		}
 
 		if ($rmode eq $symlink_mode) {
 			$symlink{$dst_path}{right} =
-				$diffrepo->command_oneline('show', "$rsha1");
+				$repo->command_oneline('show', "$rsha1");
 		}
 
 		if ($lmode ne $null_mode and $status !~ /^C/) {
-- 
2.9.0.465.g8850cbc