log-tree: show mergetag in log --show-signature output

A commit object that merges a signed tag records the "mergetag" extended
header. Check the validity of the GPG signature on it, and show it in a
way similar to how "gpgsig" extended header is shown.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/log-tree.c b/log-tree.c
index 005c5a51c08b046ed62034deeef0ea42967b1c1a..61a12a7cb01cbc36e8ed1d1a8997a8ca9bba3b05 100644 (file)
--- a/log-tree.c
+++ b/log-tree.c
@@ -443,6 +443,78 @@ static void show_signature(struct rev_info *opt, struct commit *commit)
        strbuf_release(&signature);
 }
 
+static int which_parent(const unsigned char *sha1, const struct commit *commit)
+{
+       int nth;
+       const struct commit_list *parent;
+
+       for (nth = 0, parent = commit->parents; parent; parent = parent->next) {
+               if (!hashcmp(parent->item->object.sha1, sha1))
+                       return nth;
+               nth++;
+       }
+       return -1;
+}
+
+static void show_one_mergetag(struct rev_info *opt,
+                             struct commit_extra_header *extra,
+                             struct commit *commit)
+{
+       unsigned char sha1[20];
+       struct tag *tag;
+       struct strbuf verify_message;
+       int status, nth;
+       size_t payload_size, gpg_message_offset;
+
+       hash_sha1_file(extra->value, extra->len, typename(OBJ_TAG), sha1);
+       tag = lookup_tag(sha1);
+       if (!tag)
+               return; /* error message already given */
+
+       strbuf_init(&verify_message, 256);
+       if (parse_tag_buffer(tag, extra->value, extra->len))
+               strbuf_addstr(&verify_message, "malformed mergetag\n");
+       else if ((nth = which_parent(tag->tagged->sha1, commit)) < 0)
+               strbuf_addf(&verify_message, "tag %s names a non-parent %s\n",
+                                   tag->tag, tag->tagged->sha1);
+       else
+               strbuf_addf(&verify_message,
+                           "parent #%d, tagged '%s'\n", nth + 1, tag->tag);
+       gpg_message_offset = verify_message.len;
+
+       payload_size = parse_signature(extra->value, extra->len);
+       if ((extra->len <= payload_size) ||
+           (verify_signed_buffer(extra->value, payload_size,
+                                 extra->value + payload_size,
+                                 extra->len - payload_size,
+                                 &verify_message) &&
+            verify_message.len <= gpg_message_offset)) {
+               strbuf_addstr(&verify_message, "No signature\n");
+               status = -1;
+       }
+       else if (strstr(verify_message.buf + gpg_message_offset,
+                       ": Good signature from "))
+               status = 0;
+       else
+               status = -1;
+
+       show_sig_lines(opt, status, verify_message.buf);
+       strbuf_release(&verify_message);
+}
+
+static void show_mergetag(struct rev_info *opt, struct commit *commit)
+{
+       struct commit_extra_header *extra, *to_free;
+
+       to_free = read_commit_extra_headers(commit, NULL);
+       for (extra = to_free; extra; extra = extra->next) {
+               if (strcmp(extra->key, "mergetag"))
+                       continue; /* not a merge tag */
+               show_one_mergetag(opt, extra, commit);
+       }
+       free_commit_extra_headers(to_free);
+}
+
 void show_log(struct rev_info *opt)
 {
        struct strbuf msgbuf = STRBUF_INIT;
@@ -554,8 +626,10 @@ void show_log(struct rev_info *opt)
                }
        }
 
-       if (opt->show_signature)
+       if (opt->show_signature) {
                show_signature(opt, commit);
+               show_mergetag(opt, commit);
+       }
 
        if (!commit->buffer)
                return;