[PATCH] diff: resurrect XDF_NEED_MINIMAL with --minimal

Earlier, 582aa00 (git diff too slow for a file, 2010-05-02)
unconditionally dropped XDF_NEED_MINIMAL option from the internal xdiff
invocation to help performance on pathological cases, while hinting that a
follow-up patch could reintroduce it with "--minimal" option from the
command line.

Make it so.

Signed-off-by: Junio C Hamano <redacted>
---
 * This together with René's c5aa906 (Revert removal of multi-match
   discard heuristic in 27af01, 2011-09-25) on top of v1.7.7 seems to give
   identical diff output as v1.7.1 (e.g. "git diff-tree -p v2.6.39 v3.0"
   in the kernel repository, with "--minimal").

 diff.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/diff.c b/diff.c
index 93ef9a2..34a88db 100644
--- a/diff.c
+++ b/diff.c

@@ -3511,6 +3511,10 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	}
 	else if (!strcmp(arg, "--abbrev"))
 		options->abbrev = DEFAULT_ABBREV;
+	else if (!strcmp(arg, "--minimal"))
+		DIFF_XDL_SET(options, NEED_MINIMAL);
+	else if (!strcmp(arg, "--no-minimal"))
+		DIFF_XDL_CLR(options, NEED_MINIMAL);
 	else if (!prefixcmp(arg, "--abbrev=")) {
 		options->abbrev = strtoul(arg + 9, NULL, 10);
 		if (options->abbrev < MINIMUM_ABBREV)

-- 
1.7.7