Re: [PATCH] add--interactive: respect diff.algorithm

[Junio C Hamano <gitster@pobox.com>]

John Keeping <john@keeping.me.uk> writes:

>> > +my $diff_algorithm = ($repo->config('diff.algorithm') or 'default');
>> > +
>> >  my $use_readkey = 0;
>> >  my $use_termcap = 0;
>> >  my %term_escapes;
>> > @@ -731,6 +733,9 @@ sub run_git_apply {
>> >  sub parse_diff {
>> >  	my ($path) = @_;
>> >  	my @diff_cmd = split(" ", $patch_mode_flavour{DIFF});
>> > +	if ($diff_algorithm ne "default") {
>> > +		push @diff_cmd, "--diff-algorithm=${diff_algorithm}";
>> > +	}

This is not exactly sanitary for "stash -p", whose DIFF element is
defined like so:

	'stash' => {
		DIFF => 'diff-index -p HEAD',

and you will end up appending an option after a non-option argument,

It may happen to be accepted by the command line parser which is
overly lax, but we would want to tighten it in the longer term.

As a band-aid, we could do something like the attached patch, but
for the longer term, we might need to rethink the way the tweaking
of the command line is done by $patch_mode_revision.

-- >8 --
Subject: add -i: add extra options at the right place in "diff" command line

Appending "--diff-algorithm=histogram" at the end of canned command
line for various modes of "diff" is correct for most of them but not
for "stash" that has a non-option already wired in, like so:

	'stash' => {
		DIFF => 'diff-index -p HEAD',

Appending an extra option after non-option may happen to work due to
overly lax command line parser, but that is not something we should
rely on.  Instead, splice in the extra argument immediately after a
'-p' option, which is an option to ask for textual diff output that
has to be in all variants.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 git-add--interactive.perl | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/git-add--interactive.perl b/git-add--interactive.perl
index 5310959..b50551a 100755
--- a/git-add--interactive.perl
+++ b/git-add--interactive.perl
@@ -730,11 +730,23 @@ sub run_git_apply {
 	return close $fh;
 }
 
+# The command array must have a single "-p" to ask for output in the
+# patch form.  Splice additional options immediately after it; we
+# should not be randomly appending them, as some of the canned command.
+# has non-option argument like HEAD already on it.
+
+sub splice_diff_options {
+	my $diff_cmd = shift;
+	@$diff_cmd = map {
+		($_ eq '-p') ? ($_, @_) : $_;		
+	} @$diff_cmd;
+}
+
 sub parse_diff {
 	my ($path) = @_;
 	my @diff_cmd = split(" ", $patch_mode_flavour{DIFF});
 	if (defined $diff_algorithm) {
-		push @diff_cmd, "--diff-algorithm=${diff_algorithm}";
+		splice_diff_options(\@diff_cmd, "--diff-algorithm=${diff_algorithm}");
 	}
 	if (defined $patch_mode_revision) {
 		push @diff_cmd, $patch_mode_revision;