Teach packing about "tag" objects

(And teach sha1_file and unpack-object know how to unpack them too, of
course)

pack-objects.c

@@ -6,21 +6,21 @@
 
 static const char pack_usage[] = "git-pack-objects [--window=N] [--depth=N] base-name < object-list";
 
-enum object_type {
-	OBJ_NONE,
-	OBJ_COMMIT,
-	OBJ_TREE,
-	OBJ_BLOB,
-	OBJ_DELTA
-};
-
+/*
+ * The object type is a single-character shorthand:
+ *  - 'C' for "Commit"
+ *  - 'T' for "Tree"
+ *  - 'B' for "Blob"
+ *  - 'G' for "taG"
+ *  - 'D' for "Delta"
+ */
 struct object_entry {
 	unsigned char sha1[20];
 	unsigned long size;
 	unsigned long offset;
 	unsigned int depth;
 	unsigned int hash;
-	enum object_type type;
+	unsigned char type;
 	unsigned long delta_size;
 	struct object_entry *delta;
 };
@@ -67,7 +67,7 @@ static unsigned long write_object(struct sha1file *f, struct object_entry *entry
 	 * length, except for deltas that has the 20 bytes of delta sha
 	 * instead.
 	 */
-	header[0] = ".CTB"[entry->type];
+	header[0] = entry->type;
 	hdrlen = 5;
 	if (entry->delta) {
 		header[0] = 'D';
@@ -164,11 +164,13 @@ static void check_object(struct object_entry *entry)
 
 	if (!sha1_object_info(entry->sha1, type, &entry->size)) {
 		if (!strcmp(type, "commit")) {
-			entry->type = OBJ_COMMIT;
+			entry->type = 'C';
 		} else if (!strcmp(type, "tree")) {
-			entry->type = OBJ_TREE;
+			entry->type = 'T';
 		} else if (!strcmp(type, "blob")) {
-			entry->type = OBJ_BLOB;
+			entry->type = 'B';
+		} else if (!strcmp(type, "tag")) {
+			entry->type = 'G';
 		} else
 			die("unable to pack object %s of type %s",
 			    sha1_to_hex(entry->sha1), type);

sha1_file.c

@@ -695,6 +695,9 @@ static int packed_object_info(struct pack_entry *entry,
 	case 'B':
 		strcpy(type, "blob");
 		break;
+	case 'G':
+		strcpy(type, "tag");
+		break;
 	default:
 		die("corrupted pack file");
 	}
@@ -807,6 +810,9 @@ static void *unpack_entry(struct pack_entry *entry,
 	case 'B':
 		strcpy(type, "blob");
 		break;
+	case 'G':
+		strcpy(type, "tag");
+		break;
 	default:
 		die("corrupted pack file");
 	}

unpack-objects.c

@@ -124,6 +124,7 @@ static int unpack_non_delta_entry(struct pack_entry *entry,
 	case 'C': type_s = "commit"; break;
 	case 'T': type_s = "tree"; break;
 	case 'B': type_s = "blob"; break;
+	case 'G': type_s = "tag"; break;
 	default: goto err_finish;
 	}
 	if (write_sha1_file(buffer, size, type_s, sha1) < 0)
@@ -249,7 +250,7 @@ static void unpack_entry(struct pack_entry *entry)
 	size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
 	left = pack_size - offset - 5;
 	switch (*pack) {
-	case 'C': case 'T': case 'B':
+	case 'C': case 'T': case 'B': case 'G':
 		unpack_non_delta_entry(entry, *pack, pack+5, size, left);
 		break;
 	case 'D':