Re: [PATCH 2/2] checkout: improve error messages for -b with extra argument

> When we try to create a branch "foo" based on "origin/master" and give
> git commit -b an extra unsupported argument "bar", it confusingly
> reports:
> 
>    $ git checkout -b foo origin/master bar
>    fatal: 'bar' is not a commit and a branch 'foo' cannot be created from it
> 
>    $ git checkout --track -b foo origin/master bar
>    fatal: 'bar' is not a commit and a branch 'foo' cannot be created from it
> 
> That's wrong, because it very well understands that "origin/master" is
> supposed to be the start point for the new branch and not "bar".  Check
> if we got a commit and show more fitting messages in that case instead:
> 
>    $ git checkout -b foo origin/master bar
>    fatal: Cannot update paths and switch to branch 'foo' at the same time.
> 
>    $ git checkout --track -b foo origin/master bar
>    fatal: '--track' cannot be used with updating paths

> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index e9d111bb83..24336e1017 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -1689,7 +1689,7 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
>  		 * Try to give more helpful suggestion.
>  		 * new_branch && argc > 1 will be caught later.
>  		 */
> -		if (opts->new_branch && argc == 1)
> +		if (opts->new_branch && argc == 1 && !new_branch_info.commit)
>  			die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
>  				argv[0], opts->new_branch);