git-rev-parse: re-organize and be more careful

Output default revisions as their hex SHA1 names to be consistent.

Add "--verify" flag that verifies that we output a single ref and not
more (and disables ref arguments).

rev-parse.c

@@ -6,6 +6,13 @@
 #include "cache.h"
 #include "commit.h"
 
+static char *def = NULL;
+static int no_revs = 0;
+static int single_rev = 0;
+static int revs_only = 0;
+static int do_rev_argument = 1;
+static int output_revs = 0;
+
 static int get_extended_sha1(char *name, unsigned char *sha1);
 
 /*
@@ -35,6 +42,44 @@ static int is_rev_argument(const char *arg)
 	}
 }
 
+static void show_rev(unsigned char *sha1)
+{
+	if (no_revs)
+		return;
+	output_revs++;
+	puts(sha1_to_hex(sha1));
+}
+
+static void show_antirev(unsigned char *sha1)
+{
+	if (no_revs)
+		return;
+	output_revs++;
+	printf("^%s\n", sha1_to_hex(sha1));
+}
+
+static void show_rev_arg(char *rev)
+{
+	if (no_revs)
+		return;
+	puts(rev);
+}
+
+static void show_norev(char *norev)
+{
+	if (revs_only)
+		return;
+	puts(norev);
+}
+
+static void show_arg(char *arg)
+{
+	if (do_rev_argument && is_rev_argument(arg))
+		show_rev_arg(arg);
+	else
+		show_norev(arg);
+}
+
 static int get_parent(char *name, unsigned char *result, int idx)
 {
 	unsigned char sha1[20];
@@ -85,33 +130,43 @@ static int get_extended_sha1(char *name, unsigned char *sha1)
 	return get_sha1(name, sha1);
 }
 
+static void show_default(void)
+{
+	char *s = def;
+
+	if (s) {
+		unsigned char sha1[20];
+
+		def = NULL;
+		if (!get_extended_sha1(s, sha1)) {
+			show_rev(sha1);
+			return;
+		}
+		show_arg(s);
+	}
+}
+
 int main(int argc, char **argv)
 {
-	int i, as_is = 0, revs_only = 0, no_revs = 0;
-	char *def = NULL;
+	int i, as_is = 0;
 	unsigned char sha1[20];
 
 	for (i = 1; i < argc; i++) {
 		char *arg = argv[i];
 		char *dotdot;
 
 		if (as_is) {
-			printf("%s\n", arg);
+			show_norev(arg);
 			continue;
 		}
 		if (*arg == '-') {
 			if (!strcmp(arg, "--")) {
-				if (def) {
-					printf("%s\n", def);
-					def = NULL;
-				}
+				show_default();
 				if (revs_only)
 					break;
 				as_is = 1;
 			}
 			if (!strcmp(arg, "--default")) {
-				if (def)
-					printf("%s\n", def);
 				def = argv[i+1];
 				i++;
 				continue;
@@ -124,11 +179,13 @@ int main(int argc, char **argv)
 				no_revs = 1;
 				continue;
 			}
-			if (revs_only | no_revs) {
-				if (is_rev_argument(arg) != revs_only)
-					continue;
+			if (!strcmp(arg, "--verify")) {
+				revs_only = 1;
+				do_rev_argument = 0;
+				single_rev = 1;
+				continue;
 			}
-			printf("%s\n", arg);
+			show_arg(arg);
 			continue;
 		}
 		dotdot = strstr(arg, "..");
@@ -143,8 +200,8 @@ int main(int argc, char **argv)
 					if (no_revs)
 						continue;
 					def = NULL;
-					printf("%s\n", sha1_to_hex(end));
-					printf("^%s\n", sha1_to_hex(sha1));
+					show_rev(end);
+					show_antirev(sha1);
 					continue;
 				}
 			}
@@ -154,25 +211,23 @@ int main(int argc, char **argv)
 			if (no_revs)
 				continue;
 			def = NULL;
-			printf("%s\n", sha1_to_hex(sha1));
+			show_rev(sha1);
 			continue;
 		}
 		if (*arg == '^' && !get_extended_sha1(arg+1, sha1)) {
 			if (no_revs)
 				continue;
 			def = NULL;
-			printf("^%s\n", sha1_to_hex(sha1));
+			show_antirev(sha1);
 			continue;
 		}
-		if (def) {
-			printf("%s\n", def);
-			def = NULL;
-		}
-		if (revs_only)
-			continue;
-		printf("%s\n", arg);
+		show_default();
+		show_norev(arg);
+	}
+	show_default();
+	if (single_rev && output_revs != 1) {
+		fprintf(stderr, "Needed a single revision\n");
+		exit(1);
 	}
-	if (def)
-		printf("%s\n", def);
 	return 0;
 }