Update git to v1.7.5.4

Some changes to diff options:

- no_merges has become the more general max_parents
- path restriction now uses struct pathspec

Signed-off-by: John Keeping <john@keeping.me.uk>

ui-stats.c

@@ -239,7 +239,7 @@ struct string_list collect_stats(struct cgit_context *ctx,
 	init_revisions(&rev, NULL);
 	rev.abbrev = DEFAULT_ABBREV;
 	rev.commit_format = CMIT_FMT_DEFAULT;
-	rev.no_merges = 1;
+	rev.max_parents = 1;
 	rev.verbose_header = 1;
 	rev.show_root_diff = 0;
 	setup_revisions(argc, argv, &rev, NULL);