[PATCH] Add option -b/--branch to clone for select a new HEAD

["Kirill A. Korinskiy" <catap@catap.ru>]

Sometimes (especially on production systems) we need to use only one
remote branch for building software. It really annoying to clone
origin and then swith branch by hand everytime. So this patch provide
functionality to clone remote branch with one command without using
checkout after clone.
---
 Documentation/git-clone.txt |    4 ++++
 builtin-clone.c             |   23 ++++++++++++++++++++---
 t/t5706-clone-brnach.sh     |   31 +++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 3 deletions(-)
 create mode 100755 t/t5706-clone-brnach.sh

diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
index 2c63a0f..50446d2 100644
--- a/Documentation/git-clone.txt
+++ b/Documentation/git-clone.txt
@@ -127,6 +127,10 @@ objects from the source repository into a pack in the cloned repository.
 	Instead of using the remote name 'origin' to keep track
 	of the upstream repository, use <name>.
 
+--branch <name>::
+-b <name>::
+	Instead of using the remote HEAD as master, use <name> branch.
+
 --upload-pack <upload-pack>::
 -u <upload-pack>::
 	When given, and the repository to clone from is accessed
diff --git a/builtin-clone.c b/builtin-clone.c
index 32dea74..9cea056 100644
--- a/builtin-clone.c
+++ b/builtin-clone.c
@@ -41,6 +41,7 @@ static int option_quiet, option_no_checkout, option_bare, option_mirror;
 static int option_local, option_no_hardlinks, option_shared;
 static char *option_template, *option_reference, *option_depth;
 static char *option_origin = NULL;
+static char *option_branch = NULL;
 static char *option_upload_pack = "git-upload-pack";
 static int option_verbose;
 
@@ -65,6 +66,8 @@ static struct option builtin_clone_options[] = {
 		   "reference repository"),
 	OPT_STRING('o', "origin", &option_origin, "branch",
 		   "use <branch> instead of 'origin' to track upstream"),
+	OPT_STRING('b', "branch", &option_branch, "branch",
+		   "use <branch> from 'origin' as HEAD"),
 	OPT_STRING('u', "upload-pack", &option_upload_pack, "path",
 		   "path to git-upload-pack on the remote"),
 	OPT_STRING(0, "depth", &option_depth, "depth",
@@ -347,8 +350,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	const char *repo_name, *repo, *work_tree, *git_dir;
 	char *path, *dir;
 	int dest_exists;
-	const struct ref *refs, *head_points_at, *remote_head, *mapped_refs;
-	struct strbuf key = STRBUF_INIT, value = STRBUF_INIT;
+	const struct ref *refs, *head_points_at, *remote_head = NULL, *mapped_refs;
+	struct strbuf key = STRBUF_INIT, value = STRBUF_INIT, branch_head = STRBUF_INIT;
 	struct strbuf branch_top = STRBUF_INIT, reflog_msg = STRBUF_INIT;
 	struct transport *transport = NULL;
 	char *src_ref_prefix = "refs/heads/";
@@ -518,7 +521,21 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 
 		mapped_refs = write_remote_refs(refs, refspec, reflog_msg.buf);
 
-		remote_head = find_ref_by_name(refs, "HEAD");
+		if (option_branch) {
+			strbuf_addf(&branch_head, "%s%s", src_ref_prefix, option_branch);
+
+			remote_head = find_ref_by_name(refs, branch_head.buf);
+		}
+
+		if (!remote_head) {
+			if (option_branch)
+				warning("Remote branch %s not found in upstream %s"
+					", using HEAD instead",
+					option_branch, option_origin);
+
+			remote_head = find_ref_by_name(refs, "HEAD");
+		}
+
 		head_points_at = guess_remote_head(remote_head, mapped_refs, 0);
 	}
 	else {
diff --git a/t/t5706-clone-brnach.sh b/t/t5706-clone-brnach.sh
new file mode 100755
index 0000000..1f2704b
--- /dev/null
+++ b/t/t5706-clone-brnach.sh
@@ -0,0 +1,31 @@
+#!/bin/sh
+
+test_description='branch clone options'
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+
+	mkdir parent &&
+	(cd parent && git init &&
+	 echo one >file && git add file &&
+	 git commit -m one && git checkout -b two &&
+	 echo two >f && git add f && git commit -m two &&
+	 git checkout master)
+
+'
+
+test_expect_success 'clone' '
+
+	git clone parent clone &&
+	(cd clone && git rev-parse --verify refs/remotes/origin/master)
+
+'
+
+test_expect_success 'clone -b' '
+
+	git clone -b two parent clone-b &&
+	(cd clone && git rev-parse --verify refs/remotes/origin/two)
+
+'
+
+test_done
-- 
1.6.2