[PATCH v2 11/12] commit: copy merged signed tags to headers of merge commit

[Junio C Hamano <gitster@pobox.com>]

Now MERGE_HEAD records the tag objects without peeling, we could record
the result of manual conflict resolution via "git commit" without losing
the tag information.

In hindsight, it would have been better to make "merge --continue" as the
way to continue from such an interrupted merge, not "commit", but this is
a backward compatibility baggage we would need to carry around for now.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/commit.c |   10 +++++-----
 commit.c         |   46 +++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index c46f2d1..4688a73 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1425,7 +1425,6 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 			pptr = &commit_list_insert(c->item, pptr)->next;
 	} else if (whence == FROM_MERGE) {
 		struct strbuf m = STRBUF_INIT;
-		struct commit *commit;
 		FILE *fp;
 
 		if (!reflog_msg)
@@ -1436,11 +1435,12 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 			die_errno(_("could not open '%s' for reading"),
 				  git_path("MERGE_HEAD"));
 		while (strbuf_getline(&m, fp, '\n') != EOF) {
-			unsigned char sha1[20];
-			if (get_sha1_hex(m.buf, sha1) < 0)
+			struct commit *parent;
+
+			parent = get_merge_parent(m.buf);
+			if (!parent)
 				die(_("Corrupt MERGE_HEAD file (%s)"), m.buf);
-			commit = lookup_commit_or_die(sha1, "MERGE_HEAD");
-			pptr = &commit_list_insert(commit, pptr)->next;
+			pptr = &commit_list_insert(parent, pptr)->next;
 		}
 		fclose(fp);
 		strbuf_release(&m);
diff --git a/commit.c b/commit.c
index 83ff503..7d471a3 100644
--- a/commit.c
+++ b/commit.c
@@ -840,6 +840,41 @@ struct commit_list *reduce_heads(struct commit_list *heads)
 	return result;
 }
 
+static void handle_signed_tag(struct strbuf *signed_tags, struct commit *parent)
+{
+	struct merge_remote_desc *desc;
+	struct strbuf sig = STRBUF_INIT;
+	char *buf;
+	unsigned long size, len;
+	enum object_type type;
+
+	desc = merge_remote_util(parent);
+	if (!desc || !desc->obj)
+		return;
+	buf = read_sha1_file(desc->obj->sha1, &type, &size);
+	if (!buf || type != OBJ_TAG)
+		goto free_return;
+	len = parse_signature(buf, size);
+	if (size == len)
+		goto free_return;
+	/*
+	 * We could verify this signature again and either omit writing
+	 * the contents of the tag when it does not validate, but the
+	 * integrator may not have the public key of the signer of the
+	 * tag he is merging, while a later auditor may acquire the public
+	 * key while auditing, so let's not run verify-signed-buffer here
+	 * for now...
+	 *
+	 * if (verify_signed_buffer(buf, len, buf + len, size - len, &sig))
+	 *	warn("warning: signed tag unverified.");
+	 */
+	strbuf_add_lines(signed_tags, "mergetag ", buf, size);
+
+free_return:
+	strbuf_release(&sig);
+	free(buf);
+}
+
 static const char commit_utf8_warn[] =
 "Warning: commit message does not conform to UTF-8.\n"
 "You may want to amend it after fixing the message, or set the config\n"
@@ -852,6 +887,7 @@ int commit_tree(const char *msg, unsigned char *tree,
 	int result;
 	int encoding_is_utf8;
 	struct strbuf buffer;
+	struct strbuf signed_tags = STRBUF_INIT;
 
 	assert_sha1_type(tree, OBJ_TREE);
 
@@ -868,8 +904,11 @@ int commit_tree(const char *msg, unsigned char *tree,
 	 */
 	while (parents) {
 		struct commit_list *next = parents->next;
+		struct commit *parent = parents->item;
+
 		strbuf_addf(&buffer, "parent %s\n",
-			sha1_to_hex(parents->item->object.sha1));
+			    sha1_to_hex(parent->object.sha1));
+		handle_signed_tag(&signed_tags, parent);
 		free(parents);
 		parents = next;
 	}
@@ -881,6 +920,11 @@ int commit_tree(const char *msg, unsigned char *tree,
 	strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
 	if (!encoding_is_utf8)
 		strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
+
+	if (signed_tags.len) {
+		strbuf_addbuf(&buffer, &signed_tags);
+		strbuf_release(&signed_tags);
+	}
 	strbuf_addch(&buffer, '\n');
 
 	/* And add the comment */
-- 
1.7.8.rc0.128.g31aa4