clone: allow configurable default for `-o`/`--origin`

While the default remote name of "origin" can be changed at clone-time
with `git clone`'s `--origin` option, it was previously not possible
to specify a default value for the name of that remote.  Add support for
a new `clone.defaultRemoteName` config, with the newly-created remote
name resolved in priority order:

1. (Highest priority) A remote name passed directly to `git clone -o`
2. A `clone.defaultRemoteName=new_name` in config `git clone -c`
3. A `clone.defaultRemoteName` value set in `/path/to/template/config`,
   where `--template=/path/to/template` is provided
4. A `clone.defaultRemoteName` value set in a non-template config file
5. The default value of `origin`

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Helped-by: Derrick Stolee <stolee@gmail.com>
Helped-by: Andrei Rybak <rybak.a.v@gmail.com>
Signed-off-by: Sean Barag <sean@barag.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -334,6 +334,8 @@ include::config/checkout.txt[]
 
 include::config/clean.txt[]
 
+include::config/clone.txt[]
+
 include::config/color.txt[]
 
 include::config/column.txt[]

Documentation/config/clone.txt

@@ -0,0 +1,4 @@
+clone.defaultRemoteName::
+	The name of the remote to create when cloning a repository.  Defaults to
+	`origin`, and can be overridden by passing the `--origin` command-line
+	option to linkgit:git-clone[1].

Documentation/git-clone.txt

@@ -183,8 +183,9 @@ objects from the source repository into a pack in the cloned repository.
 
 -o <name>::
 --origin <name>::
-	Instead of using the remote name `origin` to keep track
-	of the upstream repository, use `<name>`.
+	Instead of using the remote name `origin` to keep track of the upstream
+	repository, use `<name>`.  Overrides `clone.defaultRemoteName` from the
+	config.
 
 -b <name>::
 --branch <name>::

builtin/clone.c

@@ -53,7 +53,7 @@ static int option_shallow_submodules;
 static int deepen;
 static char *option_template, *option_depth, *option_since;
 static char *option_origin = NULL;
-static char *remote_name = "origin";
+static char *remote_name = NULL;
 static char *option_branch = NULL;
 static struct string_list option_not = STRING_LIST_INIT_NODUP;
 static const char *real_git_dir;
@@ -854,6 +854,10 @@ static int checkout(int submodule_progress)
 
 static int git_clone_config(const char *k, const char *v, void *cb)
 {
+	if (!strcmp(k, "clone.defaultremotename")) {
+		free(remote_name);
+		remote_name = xstrdup(v);
+	}
 	return git_default_config(k, v, cb);
 }
 
@@ -1010,12 +1014,6 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		option_no_checkout = 1;
 	}
 
-	if (option_origin)
-		remote_name = option_origin;
-
-	if (!valid_remote_name(remote_name))
-		die(_("'%s' is not a valid remote name"), remote_name);
-
 	repo_name = argv[0];
 
 	path = get_repo_path(repo_name, &is_bundle);
@@ -1158,6 +1156,19 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	 */
 	git_config(git_clone_config, NULL);
 
+	/*
+	 * apply the remote name provided by --origin only after this second
+	 * call to git_config, to ensure it overrides all config-based values.
+	 */
+	if (option_origin != NULL)
+		remote_name = xstrdup(option_origin);
+
+	if (remote_name == NULL)
+		remote_name = xstrdup("origin");
+
+	if (!valid_remote_name(remote_name))
+		die(_("'%s' is not a valid remote name"), remote_name);
+
 	if (option_bare) {
 		if (option_mirror)
 			src_ref_prefix = "refs/";
@@ -1358,6 +1369,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	junk_mode = JUNK_LEAVE_REPO;
 	err = checkout(submodule_progress);
 
+	free(remote_name);
 	strbuf_release(&reflog_msg);
 	strbuf_release(&branch_top);
 	strbuf_release(&key);

t/t5606-clone-options.sh

@@ -19,6 +19,13 @@ test_expect_success 'clone -o' '
 
 '
 
+test_expect_success 'rejects invalid -o/--origin' '
+
+	test_must_fail git clone -o "bad...name" parent clone-bad-name 2>err &&
+	test_i18ngrep "'\''bad...name'\'' is not a valid remote name" err
+
+'
+
 test_expect_success 'disallows --bare with --origin' '
 
 	test_must_fail git clone -o foo --bare parent clone-bare-o 2>err &&
@@ -63,6 +70,21 @@ test_expect_success 'prefers -c config over --template config' '
 
 '
 
+test_expect_success 'prefers config "clone.defaultRemoteName" over default' '
+
+	test_config_global clone.defaultRemoteName from_config &&
+	git clone parent clone-config-origin &&
+	git -C clone-config-origin rev-parse --verify refs/remotes/from_config/master
+
+'
+
+test_expect_success 'prefers --origin over -c config' '
+
+	git clone -c clone.defaultRemoteName=inline --origin from_option parent clone-o-and-inline-config &&
+	git -C clone-o-and-inline-config rev-parse --verify refs/remotes/from_option/master
+
+'
+
 test_expect_success 'redirected clone does not show progress' '
 
 	git clone "file://$(pwd)/parent" clone-redirected >out 2>err &&