reflog: handle the birth of a branch

The reflog append function was overzealous in its checking. When passed
an old and new ids, it should not do any checking, but just serialize
the data to a reflog entry.

src/refdb_fs.c

@@ -992,18 +992,24 @@ out:
 static int maybe_append_head(refdb_fs_backend *backend, const git_reference *ref, const git_signature *who, const char *message)
 {
 	int error;
-	git_oid old_id;
+	git_oid old_id = {{0}};
 	git_reference *head;
 
-	error = git_reference_name_to_id(&old_id, backend->repo, ref->name);
-	if (!git_branch_is_head(ref))
-		return 0;
+	/* if we can't resolve, we use {0}*40 as old id */
+	git_reference_name_to_id(&old_id, backend->repo, ref->name);
 
 	if ((error = git_reference_lookup(&head, backend->repo, "HEAD")) < 0)
 		return error;
 
+	if (git_reference_type(head) == GIT_REF_OID)
+		goto cleanup;
+
+	if (strcmp(git_reference_symbolic_target(head), ref->name))
+		goto cleanup;
+
 	error = reflog_append(backend, head, &old_id, git_reference_target(ref), who, message);
 
+cleanup:
 	git_reference_free(head);
 	return error;
 }
@@ -1595,23 +1601,23 @@ static int reflog_append(refdb_fs_backend *backend, const git_reference *ref, co
 			return error;
 	}
 
-	if (is_symbolic) {
-		error = git_reference_name_to_id(&new_id, repo, git_reference_symbolic_target(ref));
-		if (error < 0 && error != GIT_ENOTFOUND)
-			return error;
-		/* detaching HEAD does not create an entry */
-		if (error == GIT_ENOTFOUND)
-			return 0;
+	if (new) {
+		git_oid_cpy(&new_id, new);
+	} else {
+		if (!is_symbolic) {
+			git_oid_cpy(&new_id, git_reference_target(ref));
+		} else {
+			error = git_reference_name_to_id(&new_id, repo, git_reference_symbolic_target(ref));
+			if (error < 0 && error != GIT_ENOTFOUND)
+				return error;
+			/* detaching HEAD does not create an entry */
+			if (error == GIT_ENOTFOUND)
+				return 0;
 
-		giterr_clear();
+			giterr_clear();
+		}
 	}
 
-
-	if (new)
-		git_oid_cpy(&new_id, new);
-	else if (!is_symbolic)
-		git_oid_cpy(&new_id, git_reference_target(ref));
-
 	if ((error = serialize_reflog_entry(&buf, &old_id, &new_id, who, message)) < 0)
 		goto cleanup;
 

tests/repo/head.c

@@ -368,3 +368,51 @@ void test_repo_head__set_to_current_target(void)
 	git_signature_free(sig);
 
 }
+
+void test_repo_head__branch_birth(void)
+{
+	git_signature *sig;
+	git_oid id;
+	git_tree *tree;
+	git_reference *ref;
+	const char *msg;
+	git_reflog *log;
+	size_t nentries, nentries_after;
+
+	cl_git_pass(git_reflog_read(&log, repo, GIT_HEAD_FILE));
+	nentries = git_reflog_entrycount(log);
+	git_reflog_free(log);
+
+	cl_git_pass(git_signature_now(&sig, "me", "foo@example.com"));
+
+	cl_git_pass(git_repository_head(&ref, repo));
+	cl_git_pass(git_reference_peel((git_object **) &tree, ref, GIT_OBJ_TREE));
+	git_reference_free(ref);
+
+	msg = "message 1";
+	cl_git_pass(git_repository_set_head(repo, "refs/heads/orphan", sig, msg));
+
+	cl_git_pass(git_reflog_read(&log, repo, GIT_HEAD_FILE));
+	nentries_after = git_reflog_entrycount(log);
+	git_reflog_free(log);
+
+	cl_assert_equal_i(nentries, nentries_after);
+
+	msg = "message 2";
+	cl_git_pass(git_commit_create(&id, repo, "HEAD", sig, sig, NULL, msg, tree, 0, NULL));
+
+	git_tree_free(tree);
+
+	cl_git_pass(git_reflog_read(&log, repo, "refs/heads/orphan"));
+	cl_assert_equal_i(1, git_reflog_entrycount(log));
+	git_reflog_free(log);
+
+	cl_git_pass(git_reflog_read(&log, repo, GIT_HEAD_FILE));
+	nentries_after = git_reflog_entrycount(log);
+	git_reflog_free(log);
+
+	cl_assert_equal_i(nentries + 1, nentries_after);
+
+	git_signature_free(sig);
+
+}