Merge branch 'jk/add-i-highlight'

* jk/add-i-highlight:
  add--interactive: allow custom diff highlighting programs

Documentation/config.txt

@@ -1887,6 +1887,14 @@ interactive.singleKey::
 	setting is silently ignored if portable keystroke input
 	is not available; requires the Perl module Term::ReadKey.
 
+interactive.diffFilter::
+	When an interactive command (such as `git add --patch`) shows
+	a colorized diff, git will pipe the diff through the shell
+	command defined by this configuration variable. The command may
+	mark up the diff further for human consumption, provided that it
+	retains a one-to-one correspondence with the lines in the
+	original diff. Defaults to disabled (no filtering).
+
 log.abbrevCommit::
 	If true, makes linkgit:git-log[1], linkgit:git-show[1], and
 	linkgit:git-whatchanged[1] assume `--abbrev-commit`. You may

git-add--interactive.perl

@@ -45,6 +45,7 @@ my ($diff_new_color) =
 my $normal_color = $repo->get_color("", "reset");
 
 my $diff_algorithm = $repo->config('diff.algorithm');
+my $diff_filter = $repo->config('interactive.difffilter');
 
 my $use_readkey = 0;
 my $use_termcap = 0;
@@ -754,7 +755,14 @@ sub parse_diff {
 	my @diff = run_cmd_pipe("git", @diff_cmd, "--", $path);
 	my @colored = ();
 	if ($diff_use_color) {
-		@colored = run_cmd_pipe("git", @diff_cmd, qw(--color --), $path);
+		my @display_cmd = ("git", @diff_cmd, qw(--color --), $path);
+		if (defined $diff_filter) {
+			# quotemeta is overkill, but sufficient for shell-quoting
+			my $diff = join(' ', map { quotemeta } @display_cmd);
+			@display_cmd = ("$diff | $diff_filter");
+		}
+
+		@colored = run_cmd_pipe(@display_cmd);
 	}
 	my (@hunk) = { TEXT => [], DISPLAY => [], TYPE => 'header' };
 
@@ -765,7 +773,7 @@ sub parse_diff {
 		}
 		push @{$hunk[-1]{TEXT}}, $diff[$i];
 		push @{$hunk[-1]{DISPLAY}},
-			($diff_use_color ? $colored[$i] : $diff[$i]);
+			(@colored ? $colored[$i] : $diff[$i]);
 	}
 	return @hunk;
 }