Merge branch 'jk/clone-unborn-confusion' into maint

"git clone" from a repository with some ref whose HEAD is unborn
did not set the HEAD in the resulting repository correctly, which
has been corrected.
source: <YsdyLS4UFzj0j/wB@coredump.intra.peff.net>

* jk/clone-unborn-confusion:
  clone: move unborn head creation to update_head()
  clone: use remote branch if it matches default HEAD
  clone: propagate empty remote HEAD even with other branches
  clone: drop extra newline from warning message

3 files changed, 117 insertions, 39 deletions

diff --git a/builtin/clone.c b/builtin/clone.c
index 89a91b0..9e0b2b4 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -606,7 +606,7 @@ static void update_remote_refs(const struct ref *refs,
 }
 
 static void update_head(const struct ref *our, const struct ref *remote,
-			const char *msg)
+			const char *unborn, const char *msg)
 {
 	const char *head;
 	if (our && skip_prefix(our->name, "refs/heads/", &head)) {
@@ -632,6 +632,15 @@ static void update_head(const struct ref *our, const struct ref *remote,
 		 */
 		update_ref(msg, "HEAD", &remote->old_oid, NULL, REF_NO_DEREF,
 			   UPDATE_REFS_DIE_ON_ERR);
+	} else if (unborn && skip_prefix(unborn, "refs/heads/", &head)) {
+		/*
+		 * Unborn head from remote; same as "our" case above except
+		 * that we have no ref to update.
+		 */
+		if (create_symref("HEAD", unborn, NULL) < 0)
+			die(_("unable to update HEAD"));
+		if (!option_bare)
+			install_branch_config(0, head, remote_name, unborn);
 	}
 }
 
@@ -672,7 +681,7 @@ static int checkout(int submodule_progress, int filter_submodules)
 	head = resolve_refdup("HEAD", RESOLVE_REF_READING, &oid, NULL);
 	if (!head) {
 		warning(_("remote HEAD refers to nonexistent ref, "
-			  "unable to checkout.\n"));
+			  "unable to checkout"));
 		return 0;
 	}
 	if (!strcmp(head, "HEAD")) {
@@ -876,6 +885,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	const struct ref *refs, *remote_head;
 	struct ref *remote_head_points_at = NULL;
 	const struct ref *our_head_points_at;
+	char *unborn_head = NULL;
 	struct ref *mapped_refs = NULL;
 	const struct ref *ref;
 	struct strbuf key = STRBUF_INIT;
@@ -1266,51 +1276,49 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 			if (transport_fetch_refs(transport, mapped_refs))
 				die(_("remote transport reported error"));
 		}
-
-		remote_head = find_ref_by_name(refs, "HEAD");
-		remote_head_points_at =
-			guess_remote_head(remote_head, mapped_refs, 0);
-
-		if (option_branch) {
-			our_head_points_at =
-				find_remote_branch(mapped_refs, option_branch);
-
-			if (!our_head_points_at)
-				die(_("Remote branch %s not found in upstream %s"),
-				    option_branch, remote_name);
-		}
-		else
-			our_head_points_at = remote_head_points_at;
 	}
-	else {
-		const char *branch;
-		const char *ref;
-		char *ref_free = NULL;
 
-		if (option_branch)
-			die(_("Remote branch %s not found in upstream %s"),
-					option_branch, remote_name);
+	remote_head = find_ref_by_name(refs, "HEAD");
+	remote_head_points_at = guess_remote_head(remote_head, mapped_refs, 0);
 
-		warning(_("You appear to have cloned an empty repository."));
+	if (option_branch) {
+		our_head_points_at = find_remote_branch(mapped_refs, option_branch);
+		if (!our_head_points_at)
+			die(_("Remote branch %s not found in upstream %s"),
+			    option_branch, remote_name);
+	} else if (remote_head_points_at) {
+		our_head_points_at = remote_head_points_at;
+	} else if (remote_head) {
 		our_head_points_at = NULL;
-		remote_head_points_at = NULL;
-		remote_head = NULL;
-		option_no_checkout = 1;
+	} else {
+		const char *branch;
+
+		if (!mapped_refs) {
+			warning(_("You appear to have cloned an empty repository."));
+			option_no_checkout = 1;
+		}
 
 		if (transport_ls_refs_options.unborn_head_target &&
 		    skip_prefix(transport_ls_refs_options.unborn_head_target,
 				"refs/heads/", &branch)) {
-			ref = transport_ls_refs_options.unborn_head_target;
-			create_symref("HEAD", ref, reflog_msg.buf);
+			unborn_head  = xstrdup(transport_ls_refs_options.unborn_head_target);
 		} else {
 			branch = git_default_branch_name(0);
-			ref_free = xstrfmt("refs/heads/%s", branch);
-			ref = ref_free;
+			unborn_head = xstrfmt("refs/heads/%s", branch);
 		}
 
-		if (!option_bare)
-			install_branch_config(0, branch, remote_name, ref);
-		free(ref_free);
+		/*
+		 * We may have selected a local default branch name "foo",
+		 * and even though the remote's HEAD does not point there,
+		 * it may still have a "foo" branch. If so, set it up so
+		 * that we can follow the usual checkout code later.
+		 *
+		 * Note that for an empty repo we'll already have set
+		 * option_no_checkout above, which would work against us here.
+		 * But for an empty repo, find_remote_branch() can never find
+		 * a match.
+		 */
+		our_head_points_at = find_remote_branch(mapped_refs, branch);
 	}
 
 	write_refspec_config(src_ref_prefix, our_head_points_at,
@@ -1330,7 +1338,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 			   branch_top.buf, reflog_msg.buf, transport,
 			   !is_local);
 
-	update_head(our_head_points_at, remote_head, reflog_msg.buf);
+	update_head(our_head_points_at, remote_head, unborn_head, reflog_msg.buf);
 
 	/*
 	 * We want to show progress for recursive submodule clones iff
@@ -1357,6 +1365,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	strbuf_release(&key);
 	free_refs(mapped_refs);
 	free_refs(remote_head_points_at);
+	free(unborn_head);
 	free(dir);
 	free(path);
 	UNLEAK(repo);
diff --git a/t/t5605-clone-local.sh b/t/t5605-clone-local.sh
index 21ab619..38b850c 100755
--- a/t/t5605-clone-local.sh
+++ b/t/t5605-clone-local.sh
@@ -21,7 +21,9 @@ test_expect_success 'preparing origin repository' '
 	git bundle create b2.bundle main &&
 	mkdir dir &&
 	cp b1.bundle dir/b3 &&
-	cp b1.bundle b4
+	cp b1.bundle b4 &&
+	git branch not-main main &&
+	git bundle create b5.bundle not-main
 '
 
 test_expect_success 'local clone without .git suffix' '
@@ -83,11 +85,19 @@ test_expect_success 'bundle clone from b4.bundle that does not exist' '
 	test_must_fail git clone b4.bundle bb
 '
 
-test_expect_success 'bundle clone with nonexistent HEAD' '
+test_expect_success 'bundle clone with nonexistent HEAD (match default)' '
 	git clone b2.bundle b2 &&
 	(cd b2 &&
 	git fetch &&
-	test_must_fail git rev-parse --verify refs/heads/main)
+	git rev-parse --verify refs/heads/main)
+'
+
+test_expect_success 'bundle clone with nonexistent HEAD (no match default)' '
+	git clone b5.bundle b5 &&
+	(cd b5 &&
+	git fetch &&
+	test_must_fail git rev-parse --verify refs/heads/main &&
+	test_must_fail git rev-parse --verify refs/heads/not-main)
 '
 
 test_expect_success 'clone empty repository' '
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index 00ce9ae..5d42a35 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -250,6 +250,65 @@ test_expect_success 'bare clone propagates empty default branch' '
 	grep "refs/heads/mydefaultbranch" file_empty_child.git/HEAD
 '
 
+test_expect_success 'clone propagates unborn HEAD from non-empty repo' '
+	test_when_finished "rm -rf file_unborn_parent file_unborn_child" &&
+
+	git init file_unborn_parent &&
+	(
+		cd file_unborn_parent &&
+		git checkout -b branchwithstuff &&
+		test_commit --no-tag stuff &&
+		git symbolic-ref HEAD refs/heads/mydefaultbranch
+	) &&
+
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=main -c protocol.version=2 \
+		clone "file://$(pwd)/file_unborn_parent" \
+		file_unborn_child 2>stderr &&
+	grep "refs/heads/mydefaultbranch" file_unborn_child/.git/HEAD &&
+	grep "warning: remote HEAD refers to nonexistent ref" stderr
+'
+
+test_expect_success 'bare clone propagates unborn HEAD from non-empty repo' '
+	test_when_finished "rm -rf file_unborn_parent file_unborn_child.git" &&
+
+	git init file_unborn_parent &&
+	(
+		cd file_unborn_parent &&
+		git checkout -b branchwithstuff &&
+		test_commit --no-tag stuff &&
+		git symbolic-ref HEAD refs/heads/mydefaultbranch
+	) &&
+
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=main -c protocol.version=2 \
+		clone --bare "file://$(pwd)/file_unborn_parent" \
+		file_unborn_child.git 2>stderr &&
+	grep "refs/heads/mydefaultbranch" file_unborn_child.git/HEAD &&
+	! grep "warning:" stderr
+'
+
+test_expect_success 'defaulted HEAD uses remote branch if available' '
+	test_when_finished "rm -rf file_unborn_parent file_unborn_child" &&
+
+	git init file_unborn_parent &&
+	(
+		cd file_unborn_parent &&
+		git config lsrefs.unborn ignore &&
+		git checkout -b branchwithstuff &&
+		test_commit --no-tag stuff &&
+		git symbolic-ref HEAD refs/heads/mydefaultbranch
+	) &&
+
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=branchwithstuff -c protocol.version=2 \
+		clone "file://$(pwd)/file_unborn_parent" \
+		file_unborn_child 2>stderr &&
+	grep "refs/heads/branchwithstuff" file_unborn_child/.git/HEAD &&
+	test_path_is_file file_unborn_child/stuff.t &&
+	! grep "warning:" stderr
+'
+
 test_expect_success 'fetch with file:// using protocol v2' '
 	test_when_finished "rm -f log" &&