[PATCH v2 09/12] clone: handle overridden main branch names

From: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: don@goodman-wilson.com, stolee@gmail.com, peff@peff.net,
	sandals@crustytoothpaste.net, Matt Rogers <mattr94@gmail.com>,
	Eric Sunshine <sunshine@sunshineco.com>,
	Taylor Blau <me@ttaylorr.com>,
	Phillip Wood <phillip.wood123@gmail.com>,
	Alban Gruin <alban.gruin@gmail.com>, Johannes Sixt <j6t@kdbg.org>,
	Johannes Schindelin <johannes.schindelin@gmx.de>,
	Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: [PATCH v2 09/12] clone: handle overridden main branch names
Date: Mon, 15 Jun 2020 12:50:13 +0000	[thread overview]
Message-ID: <0e59b6181699abe17eb46fe3ca5a48ce71889780.1592225416.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.656.v2.git.1592225416.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

When cloning a repository without any branches, Git chooses a default
branch name for the as-yet unborn branch.

As part of the implicit initialization of the local repository, Git
just learned to respect `init.defaultBranch` to choose a different main
branch name. We now really want that branch name to be used as a
fall-back.

At the same time, we also want to make sure that `core.mainBranch` is
set correctly, reflecting the name of the main branch. In case we detect
a main branch, we do have to do that explicitly, otherwise `init_db()`
will already have done that for us.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 Documentation/config/init.txt |  4 ++--
 builtin/clone.c               | 16 +++++++++++++---
 t/t5606-clone-options.sh      | 17 +++++++++++++++++
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/Documentation/config/init.txt b/Documentation/config/init.txt
index 6ae4a38416e..dc77f8c8446 100644
--- a/Documentation/config/init.txt
+++ b/Documentation/config/init.txt
@@ -3,5 +3,5 @@ init.templateDir::
 	(See the "TEMPLATE DIRECTORY" section of linkgit:git-init[1].)
 
 init.defaultBranch::
-	Allows overriding the default branch name when initializing
-	a new repository.
+	Allows overriding the default branch name e.g. when initializing
+	a new repository or when cloning an empty repository.
diff --git a/builtin/clone.c b/builtin/clone.c
index 487b0a42d75..755fcaeb0ba 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -718,6 +718,7 @@ static void update_head(const struct ref *our, const struct ref *remote,
 		/* Local default branch link */
 		if (create_symref("HEAD", our->name, NULL) < 0)
 			die(_("unable to update HEAD"));
+		git_config_set("core.mainbranch", head);
 		if (!option_bare) {
 			update_ref(msg, "HEAD", &our->old_oid, NULL, 0,
 				   UPDATE_REFS_DIE_ON_ERR);
@@ -1264,9 +1265,18 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		remote_head_points_at = NULL;
 		remote_head = NULL;
 		option_no_checkout = 1;
-		if (!option_bare)
-			install_branch_config(0, "master", option_origin,
-					      "refs/heads/master");
+		if (!option_bare) {
+			char *main_branch =
+				git_main_branch_name(MAIN_BRANCH_FULL_NAME);
+			const char *nick;
+
+			if (!skip_prefix(main_branch, "refs/heads/", &nick))
+				BUG("unexpected default branch '%s'",
+				    main_branch);
+			install_branch_config(0, nick, option_origin,
+					      main_branch);
+			free(main_branch);
+		}
 	}
 
 	write_refspec_config(src_ref_prefix, our_head_points_at,
diff --git a/t/t5606-clone-options.sh b/t/t5606-clone-options.sh
index 9e24ec88e67..98b2d8527f6 100755
--- a/t/t5606-clone-options.sh
+++ b/t/t5606-clone-options.sh
@@ -35,4 +35,21 @@ test_expect_success 'redirected clone -v does show progress' '
 
 '
 
+test_expect_success 'chooses correct default main branch name' '
+	git init --bare empty &&
+	git -c init.defaultBranch=up clone empty whats-up &&
+	test refs/heads/up = $(git -C whats-up symbolic-ref HEAD) &&
+	test up = $(git -C whats-up config core.mainBranch) &&
+	test refs/heads/up = $(git -C whats-up config branch.up.merge)
+'
+
+test_expect_success 'guesses main branch name correctly' '
+	git init --main-branch=guess main-branch &&
+	test_commit -C main-branch no-spoilers &&
+	git -C main-branch branch abc guess &&
+	git clone main-branch is-it &&
+	test guess = $(git -C is-it config core.mainBranch) &&
+	test refs/heads/guess = $(git -C is-it symbolic-ref HEAD)
+'
+
 test_done
-- 
gitgitgadget

