Re: [PATCH v2] var: add GIT_DEFAULT_BRANCH variable

> Introduce the builtin variable GIT_DEFAULT_BRANCH which represents the
> the default branch name that will be used by git-init.
>
> Currently this variable is equivalent to
>     git config init.defaultbranch || 'master'
>
> This however will break if at one point the default branch is changed as
> indicated by `default_branch_name_advice` in `refs.c`.
>
> By providing this command ahead of time users of git can make their
> code forward-compatible.
>
> Co-developed-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
> ---
>
> Changes from v1 ( https://lore.kernel.org/git/20211030140112.834650-1-thomas@t-8ch.de/ ):
> * Replaced the custom subcommand with an internal variable
> * Cleaned up the tests
>
> @Johannes: I replaced BUG() with die() from your example because that seems to be
> nicer for user facing messages.
>
>  Documentation/git-var.txt |  3 +++
>  builtin/var.c             | 13 +++++++++++++
>  t/t0007-git-var.sh        | 19 +++++++++++++++++++
>  3 files changed, 35 insertions(+)
>
> diff --git a/Documentation/git-var.txt b/Documentation/git-var.txt
> index 6072f936ab..387cc1b914 100644
> --- a/Documentation/git-var.txt
> +++ b/Documentation/git-var.txt
> @@ -59,6 +59,9 @@ ifdef::git-default-pager[]
>      The build you are using chose '{git-default-pager}' as the default.
>  endif::git-default-pager[]
>  
> +GIT_DEFAULT_BRANCH::
> +    The name of the first branch created in newly initialized repositories.
> +
>  SEE ALSO
>  --------
>  linkgit:git-commit-tree[1]
> diff --git a/builtin/var.c b/builtin/var.c
> index 6c6f46b4ae..d1d82b6c93 100644
> --- a/builtin/var.c
> +++ b/builtin/var.c
> @@ -5,6 +5,7 @@
>   */
>  #include "builtin.h"
>  #include "config.h"
> +#include "refs.h"
>  
>  static const char var_usage[] = "git var (-l | <variable>)";
>  
> @@ -27,6 +28,17 @@ static const char *pager(int flag)
>  	return pgm;
>  }
>  
> +static const char *default_branch(int flag)
> +{
> +	const char *name = repo_default_branch_name(the_repository, 1);
> +
> +	if (!name)
> +		die("could not determine the default branch name");