[PATCH v5 3/3] clone: respect remote unborn HEAD

From

JTJonathan Tan <jonathantanmy@google.com>

Date

Jan 26, 2021, 18:55 UTC

Message-ID

<922e8c229c359c15f1265876e6def87d7a18b763.1611686656.git.jonathantanmy@google.com>

In-Reply-To

<cover.1611686656.git.jonathantanmy@google.com>

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/config/init.txt |  2 +-
 builtin/clone.c               | 16 ++++++++++++++--
 connect.c                     | 28 ++++++++++++++++++++++++++--
 t/t5606-clone-options.sh      |  8 +++++---
 t/t5702-protocol-v2.sh        | 25 +++++++++++++++++++++++++
 transport.h                   |  8 ++++++++
 6 files changed, 79 insertions(+), 8 deletions(-)

diff --git a/Documentation/config/init.txt b/Documentation/config/init.txt
index dc77f8c844..79c79d6617 100644
--- a/Documentation/config/init.txt
+++ b/Documentation/config/init.txt
@@ -4,4 +4,4 @@ init.templateDir::
 
 init.defaultBranch::
 	Allows overriding the default branch name e.g. when initializing
-	a new repository or when cloning an empty repository.
+	a new repository.
diff --git a/builtin/clone.c b/builtin/clone.c
index 211d4f54b0..77fdc61f4d 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -1330,10 +1330,21 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		remote_head = NULL;
 		option_no_checkout = 1;
 		if (!option_bare) {
-			const char *branch = git_default_branch_name();
-			char *ref = xstrfmt("refs/heads/%s", branch);
+			const char *branch;
+			char *ref;
+
+			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;
+				transport_ls_refs_options.unborn_head_target = NULL;
+			} else {
+				branch = git_default_branch_name();
+				ref = xstrfmt("refs/heads/%s", branch);
+			}
 
 			install_branch_config(0, branch, remote_name, ref);
+			create_symref("HEAD", ref, "");
 			free(ref);
 		}
 	}
@@ -1385,5 +1396,6 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	junk_mode = JUNK_LEAVE_ALL;
 
 	strvec_clear(&transport_ls_refs_options.ref_prefixes);
+	free(transport_ls_refs_options.unborn_head_target);
 	return err;
 }
diff --git a/connect.c b/connect.c
index 328c279250..879669df93 100644
--- a/connect.c
+++ b/connect.c
@@ -376,7 +376,8 @@ struct ref **get_remote_heads(struct packet_reader *reader,
 }
 
 /* Returns 1 when a valid ref has been added to `list`, 0 otherwise */
-static int process_ref_v2(struct packet_reader *reader, struct ref ***list)
+static int process_ref_v2(struct packet_reader *reader, struct ref ***list,
+			  char **unborn_head_target)
 {
 	int ret = 1;
 	int i = 0;
@@ -397,6 +398,25 @@ static int process_ref_v2(struct packet_reader *reader, struct ref ***list)
 		goto out;
 	}
 
+	if (!strcmp("unborn", line_sections.items[i].string)) {
+		i++;
+		if (unborn_head_target &&
+		    !strcmp("HEAD", line_sections.items[i++].string)) {
+			/*
+			 * Look for the symref target (if any). If found,
+			 * return it to the caller.
+			 */
+			for (; i < line_sections.nr; i++) {
+				const char *arg = line_sections.items[i].string;
+
+				if (skip_prefix(arg, "symref-target:", &arg)) {
+					*unborn_head_target = xstrdup(arg);
+					break;
+				}
+			}
+		}
+		goto out;
+	}
 	if (parse_oid_hex_algop(line_sections.items[i++].string, &old_oid, &end, reader->hash_algo) ||
 	    *end) {
 		ret = 0;
@@ -461,6 +481,8 @@ struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 	const char *hash_name;
 	struct strvec *ref_prefixes = transport_options ?
 		&transport_options->ref_prefixes : NULL;
+	char **unborn_head_target = transport_options ?
+		&transport_options->unborn_head_target : NULL;
 	*list = NULL;
 
 	if (server_supports_v2("ls-refs", 1))
@@ -490,6 +512,8 @@ struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 	if (!for_push)
 		packet_write_fmt(fd_out, "peel\n");
 	packet_write_fmt(fd_out, "symrefs\n");
+	if (server_supports_feature("ls-refs", "unborn", 0))
+		packet_write_fmt(fd_out, "unborn\n");
 	for (i = 0; ref_prefixes && i < ref_prefixes->nr; i++) {
 		packet_write_fmt(fd_out, "ref-prefix %s\n",
 				 ref_prefixes->v[i]);
@@ -498,7 +522,7 @@ struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 
 	/* Process response from server */
 	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
-		if (!process_ref_v2(reader, &list))
+		if (!process_ref_v2(reader, &list, unborn_head_target))
 			die(_("invalid ls-refs response: %s"), reader->line);
 	}
 
diff --git a/t/t5606-clone-options.sh b/t/t5606-clone-options.sh
index 7f082fb23b..0111d4e8bd 100755
--- a/t/t5606-clone-options.sh
+++ b/t/t5606-clone-options.sh
@@ -102,11 +102,13 @@ test_expect_success 'redirected clone -v does show progress' '
 '
 
 test_expect_success 'chooses correct default initial branch name' '
-	git init --bare empty &&
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=foo init --bare empty &&
+	test_config -C empty lsrefs.allowUnborn true &&
 	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
 	git -c init.defaultBranch=up clone empty whats-up &&
-	test refs/heads/up = $(git -C whats-up symbolic-ref HEAD) &&
-	test refs/heads/up = $(git -C whats-up config branch.up.merge)
+	test refs/heads/foo = $(git -C whats-up symbolic-ref HEAD) &&
+	test refs/heads/foo = $(git -C whats-up config branch.foo.merge)
 '
 
 test_expect_success 'guesses initial branch name correctly' '
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index 7d5b17909b..a8ef92b644 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -209,6 +209,31 @@ test_expect_success 'clone with file:// using protocol v2' '
 	grep "ref-prefix refs/tags/" log
 '
 
+test_expect_success 'clone of empty repo propagates name of default branch' '
+	test_when_finished "rm -rf file_empty_parent file_empty_child" &&
+
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=mydefaultbranch init file_empty_parent &&
+
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=main -c protocol.version=2 \
+		clone "file://$(pwd)/file_empty_parent" file_empty_child &&
+	grep "refs/heads/mydefaultbranch" file_empty_child/.git/HEAD
+'
+
+test_expect_success '...but not if explicitly forbidden by config' '
+	test_when_finished "rm -rf file_empty_parent file_empty_child" &&
+
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=mydefaultbranch init file_empty_parent &&
+	test_config -C file_empty_parent lsrefs.allowUnborn false &&
+
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=main -c protocol.version=2 \
+		clone "file://$(pwd)/file_empty_parent" file_empty_child &&
+	! grep "refs/heads/mydefaultbranch" file_empty_child/.git/HEAD
+'
+
 test_expect_success 'fetch with file:// using protocol v2' '
 	test_when_finished "rm -f log" &&
 
diff --git a/transport.h b/transport.h
index 1f5b60e4d3..24e15799e7 100644
--- a/transport.h
+++ b/transport.h
@@ -243,6 +243,14 @@ struct transport_ls_refs_options {
 	 * provided ref_prefixes.
 	 */
 	struct strvec ref_prefixes;
+
+	/*
+	 * If unborn_head_target is not NULL, and the remote reports HEAD as
+	 * pointing to an unborn branch, transport_get_remote_refs() stores the
+	 * unborn branch in unborn_head_target. It should be freed by the
+	 * caller.
+	 */
+	char *unborn_head_target;
 };
 #define TRANSPORT_LS_REFS_OPTIONS_INIT { STRVEC_INIT }
 

-- 
2.30.0.280.ga3ce27912f-goog