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

["Björn Steinbrink" <B.Steinbrink@gmx.de>]

On 2009.08.25 23:27:47 +0400, Kirill A. Korinskiy wrote:
> Sometimes (especially on production systems) we need to use only one
> remote branch for building software. It's really annoying to clone
> origin and then switch branch by hand everytime. So this patch
> provides functionality to clone a remote branch with one command
> without using checkout after clone.
> 
> Signed-off-by: Kirill A. Korinskiy <catap@catap.ru>
> ---
>  Documentation/git-clone.txt |    4 ++++
>  builtin-clone.c             |   23 ++++++++++++++++++++---
>  t/t5706-clone-branch.sh     |   31 +++++++++++++++++++++++++++++++
>  3 files changed, 55 insertions(+), 3 deletions(-)
>  create mode 100755 t/t5706-clone-branch.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.

Hm, that's no good. The branch won't be called master, nor is HEAD used
as "master" anyway. If the remote repo's HEAD references refs/heads/foo,
you'll get refs/heads/foo locally as well, not "master", but see below.

Maybe: Create a local branch head for <name> instead of the branch
referenced by the remote repo's HEAD.

> @@ -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"),

Using 'origin' there is unfortunate, as using "--origin foo" would make
clone call the remote "foo" instead of "origin". And it's not really
used "as" HEAD, but instead of the remote repo's HEAD to determine which
local branch head to create. Though I guess this affect the
refs/remotes/<remote>/HEAD symref as well?

> @@ -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);

This would still pick refs/heads/master if refs/heads/master and
refs/heads/<branch> reference the same commit. That's due to the check
in guess_remote_head() which prefers refs/heads/master over all other
refs. While this is acceptable for the HEAD lookup, I'd treat that as a
bug for this new option.

>  	}
>  	else {
> diff --git a/t/t5706-clone-branch.sh b/t/t5706-clone-branch.sh
> new file mode 100755
> index 0000000..8d83ac8
> --- /dev/null
> +++ b/t/t5706-clone-branch.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-b && test $(git rev-parse --verify HEAD) = $(git rev-parse --verify refs/remotes/origin/two))

This should probably check not just that HEAD resolves to the same
commit as refs/remotes/origin/two, but that HEAD references
refs/heads/two as well, even if the remote's refs/heads/master
references the same commit as refs/heads/two (see above).

Björn