fast-import: make tagger information optional

Even though newer Porcelain tools always record the tagger information
when creating new tags, export/import pair should be able to faithfully
reproduce ancient tag objects that lack tagger information.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Acked-by: Shawn O. Pearce <spearce@spearce.org>

fast-import.c

@@ -43,7 +43,7 @@ Format of STDIN stream:
 
   new_tag ::= 'tag' sp tag_str lf
     'from' sp (ref_str | hexsha1 | sha1exp_str | idnum) lf
-    'tagger' sp name '<' email '>' when lf
+    ('tagger' sp name '<' email '>' when lf)?
     tag_msg;
   tag_msg ::= data;
 
@@ -2264,23 +2264,27 @@ static void parse_new_tag(void)
 	read_next_command();
 
 	/* tagger ... */
-	if (prefixcmp(command_buf.buf, "tagger "))
-		die("Expected tagger command, got %s", command_buf.buf);
+	if (!prefixcmp(command_buf.buf, "tagger ")) {
 		tagger = parse_ident(command_buf.buf + 7);
+		read_next_command();
+	} else
+		tagger = NULL;
 
 	/* tag payload/message */
-	read_next_command();
 	parse_data(&msg);
 
 	/* build the tag object */
 	strbuf_reset(&new_data);
+
 	strbuf_addf(&new_data,
 		    "object %s\n"
 		    "type %s\n"
-		"tag %s\n"
-		"tagger %s\n"
-		"\n",
-		sha1_to_hex(sha1), commit_type, t->name, tagger);
+		    "tag %s\n",
+		    sha1_to_hex(sha1), commit_type, t->name);
+	if (tagger)
+		strbuf_addf(&new_data,
+			    "tagger %s\n", tagger);
+	strbuf_addch(&new_data, '\n');
 	strbuf_addbuf(&new_data, &msg);
 	free(tagger);
 

t/t9300-fast-import.sh

@@ -56,6 +56,12 @@ M 644 :2 file2
 M 644 :3 file3
 M 755 :4 file4
 
+tag series-A
+from :5
+data <<EOF
+An annotated tag without a tagger
+EOF
+
 INPUT_END
 test_expect_success \
     'A: create pack from stdin' \
@@ -101,6 +107,18 @@ test_expect_success \
 	'A: verify file4' \
 	'git cat-file blob master:file4 >actual && test_cmp expect actual'
 
+cat >expect <<EOF
+object $(git rev-parse refs/heads/master)
+type commit
+tag series-A
+
+An annotated tag without a tagger
+EOF
+test_expect_success 'A: verify tag/series-A' '
+	git cat-file tag tags/series-A >actual &&
+	test_cmp expect actual
+'
+
 cat >expect <<EOF
 :2 `git rev-parse --verify master:file2`
 :3 `git rev-parse --verify master:file3`