git-rev-list: add "end" commit and "--header" flag

The "end" commit is just faking it right now, it's sorting things
purely by date, so this is _not_ a reachability analysis. Some day.

The "--header" flag causes the commit message to be printed out,
with a NUL character separator after it for parseability. This
allows you to do things like use "grep -z" to grep for certain
authors etc.

rev-list.c

 #include "cache.h"
 #include "commit.h"
 
+static const char rev_list_usage[] =
+	"usage: git-rev-list [OPTION] commit-id <commit-id>\n"
+		      "  --max-count=nr\n"
+		      "  --max-age=epoch\n"
+		      "  --min-age=epoch\n"
+		      "  --header";
+
 int main(int argc, char **argv)
 {
-	unsigned char sha1[20];
+	int nr_sha;
+	unsigned char sha1[2][20];
 	struct commit_list *list = NULL;
-	struct commit *commit;
-	char *commit_arg = NULL;
-	int i;
+	struct commit *commit, *end;
+	int i, verbose_header = 0;
 	unsigned long max_age = -1;
 	unsigned long min_age = -1;
 	int max_count = -1;
 
+	nr_sha = 0;
 	for (i = 1 ; i < argc; i++) {
 		char *arg = argv[i];
 
 		if (!strncmp(arg, "--max-count=", 12)) {
 			max_count = atoi(arg + 12);
-		} else if (!strncmp(arg, "--max-age=", 10)) {
+			continue;
+		}
+		if (!strncmp(arg, "--max-age=", 10)) {
 			max_age = atoi(arg + 10);
-		} else if (!strncmp(arg, "--min-age=", 10)) {
+			continue;
+		}
+		if (!strncmp(arg, "--min-age=", 10)) {
 			min_age = atoi(arg + 10);
-		} else {
-			commit_arg = arg;
+			continue;
 		}
+		if (!strcmp(arg, "--header")) {
+			verbose_header = 1;
+			continue;
+		}
+
+		if (nr_sha > 2 || get_sha1(arg, sha1[nr_sha]))
+			usage(rev_list_usage);
+		nr_sha++;
 	}
 
-	if (!commit_arg || get_sha1(commit_arg, sha1))
-		usage("usage: git-rev-list [OPTION] commit-id\n"
-		      "  --max-count=nr\n"
-		      "  --max-age=epoch\n"
-		      "  --min-age=epoch\n");
+	if (!nr_sha)
+		usage(rev_list_usage);
 
-	commit = lookup_commit(sha1);
+	commit = lookup_commit_reference(sha1[0]);
 	if (!commit || parse_commit(commit) < 0)
-		die("bad commit object");
+		die("bad starting commit object");
+
+	end = NULL;
+	if (nr_sha > 1) {
+		end = lookup_commit_reference(sha1[1]);
+		if (!end || parse_commit(end) < 0)
+			die("bad ending commit object");
+	}
 
 	commit_list_insert(commit, &list);
 	do {
 		struct commit *commit = pop_most_recent_commit(&list, 0x1);
 
+		if (commit == end)
+			break;
 		if (min_age != -1 && (commit->date > min_age))
 			continue;
 		if (max_age != -1 && (commit->date < max_age))
@@ -47,6 +72,8 @@ int main(int argc, char **argv)
 		if (max_count != -1 && !max_count--)
 			break;
 		printf("%s\n", sha1_to_hex(commit->object.sha1));
+		if (verbose_header)
+			printf("%s%c", commit->buffer, 0);
 	} while (list);
 	return 0;
 }