rev-list: allow -<n> as shorthand for --max-count=<n>

This builds on top of the previous one.

Traditionally, head(1) and tail(1) allow their line limits to be
parsed this way.
Signed-off-by: NEric Wong <normalperson@yhbt.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

rev-list.c

@@ -749,6 +749,11 @@ int main(int argc, const char **argv)
 		struct commit *commit;
 		unsigned char sha1[20];
 
+		/* accept -<digit>, like traditilnal "head" */
+		if ((*arg == '-') && isdigit(arg[1])) {
+			max_count = atoi(arg + 1);
+			continue;
+		}
 		if (!strcmp(arg, "-n")) {
 			if (++i >= argc)
 				die("-n requires an argument");

rev-parse.c

@@ -53,6 +53,10 @@ static int is_rev_argument(const char *arg)
 	};
 	const char **p = rev_args;
 
+	/* accept -<digit>, like traditional "head" */
+	if ((*arg == '-') && isdigit(arg[1]))
+		return 1;
+
 	for (;;) {
 		const char *str = *p++;
 		int len;