Merge pull request libgit2#2144 from linquize/branch-f-current

Do not allow git_branch_create() to force update branch

src/branch.c

@@ -58,14 +58,27 @@ int git_branch_create(
 	const git_signature *signature,
 	const char *log_message)
 {
+	int is_head = 0;
 	git_reference *branch = NULL;
 	git_buf canonical_branch_name = GIT_BUF_INIT,
 			  log_message_buf = GIT_BUF_INIT;
 	int error = -1;
 
 	assert(branch_name && commit && ref_out);
 	assert(git_object_owner((const git_object *)commit) == repository);
+	if (git_branch_lookup(&branch, repository, branch_name, GIT_BRANCH_LOCAL) == 0) {
+		if ((is_head = git_branch_is_head(branch)) < 0) {
+			error = is_head;
+			goto cleanup;
+		}
+	}
 
+	if (is_head && force) {
+		giterr_set(GITERR_REFERENCE, "Cannot force update branch '%s' as it is "
+			"the current HEAD of the repository.", git_reference_name(branch));
+		goto cleanup;
+	}
+
 	if (git_buf_joinpath(&canonical_branch_name, GIT_REFS_HEADS_DIR, branch_name) < 0)
 		goto cleanup;
 

tests/refs/branches/create.c

@@ -67,6 +67,25 @@ void test_refs_branches_create__can_force_create_over_an_existing_branch(void)
 	cl_assert_equal_s("refs/heads/br2", git_reference_name(branch));
 }
 
+void test_refs_branches_create__cannot_force_create_over_current_branch(void)
+{
+	const git_oid *oid;
+	git_reference *branch2;
+	retrieve_known_commit(&target, repo);
+
+	cl_git_pass(git_branch_lookup(&branch2, repo, "master", GIT_BRANCH_LOCAL));
+	cl_assert_equal_s("refs/heads/master", git_reference_name(branch2));
+	cl_assert_equal_i(true, git_branch_is_head(branch2));
+	oid = git_reference_target(branch2);
+
+	cl_git_fail_with(-1, git_branch_create(&branch, repo, "master", target, 1, NULL, NULL));
+	branch = NULL;
+	cl_git_pass(git_branch_lookup(&branch, repo, "master", GIT_BRANCH_LOCAL));
+	cl_assert_equal_s("refs/heads/master", git_reference_name(branch));
+	cl_git_pass(git_oid_cmp(git_reference_target(branch), oid));
+	git_reference_free(branch2);
+}
+
 void test_refs_branches_create__creating_a_branch_with_an_invalid_name_returns_EINVALIDSPEC(void)
 {
 	retrieve_known_commit(&target, repo);