Re: [PATCH v4 15/21] init: allow alternate ref strorage to be set for new repos

> git init learns a new argument --ref-storage.  Presently, only
> "files" is supported, but later we will add other storage backends.
> 
> When this argument is used, the repository's extensions.refStorage
> configuration value is set (as well as core.repositoryformatversion),
> and the ref storage backend's initdb function is used to set up the
> ref database.
> 
> Signed-off-by: David Turner <dturner@twopensource.com>
> Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
> ---
>  Documentation/git-init-db.txt          |  2 +-
>  Documentation/git-init.txt             |  7 +++++-
>  builtin/init-db.c                      | 44 +++++++++++++++++++++++++++-------
>  cache.h                                |  2 ++
>  contrib/completion/git-completion.bash |  3 ++-
>  path.c                                 | 29 ++++++++++++++++++++--
>  refs.c                                 |  8 +++++++
>  refs.h                                 |  8 +++++++
>  setup.c                                | 12 ++++++++++
>  t/t0001-init.sh                        | 25 +++++++++++++++++++
>  10 files changed, 127 insertions(+), 13 deletions(-)
> 
> [...]
> diff --git a/Documentation/git-init.txt b/Documentation/git-init.txt
> index 8174d27..d2b150f 100644
> --- a/Documentation/git-init.txt
> +++ b/Documentation/git-init.txt
> @@ -12,7 +12,7 @@ SYNOPSIS
>  'git init' [-q | --quiet] [--bare] [--template=<template_directory>]
>  	  [--separate-git-dir <git dir>]
>  	  [--shared[=<permissions>]] [directory]
> -
> +	  [--ref-storage=<name>]
>  
>  DESCRIPTION
>  -----------
> @@ -113,6 +113,11 @@ does not exist, it will be created.
>  
>  --
>  
> +--ref-storage=<name>::
> +Type of refs storage backend. Default is to use the original "files"
> +storage, which stores ref data in files in .git/refs and
> +.git/packed-refs.
> +

>  TEMPLATE DIRECTORY
>  ------------------
>  
> diff --git a/builtin/init-db.c b/builtin/init-db.c
> index 801e977..d331ce8 100644
> --- a/builtin/init-db.c
> +++ b/builtin/init-db.c
> @@ -24,6 +24,7 @@ static int init_is_bare_repository = 0;
>  static int init_shared_repository = -1;
>  static const char *init_db_template_dir;
>  static const char *git_link;
> +static char *requested_ref_storage_backend;
>  
>  static void copy_templates_1(struct strbuf *path, struct strbuf *template,
>  			     DIR *dir)
> @@ -179,6 +180,7 @@ static int create_default_files(const char *template_path)
>  	int reinit;
>  	int filemode;
>  	struct strbuf err = STRBUF_INIT;
> +	int repo_version = 0;
>  
>  	/* Just look for `init.templatedir` */
>  	git_config(git_init_db_config, NULL);
> @@ -205,6 +207,32 @@ static int create_default_files(const char *template_path)
>  	}
>  
>  	/*
> +	 * Create the default symlink from ".git/HEAD" to the "master"

> +	 * branch, if it does not exist yet.
> +	 */
> [...]
> diff --git a/setup.c b/setup.c
> index 0deb022..1a62277 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -1,5 +1,6 @@
>  #include "cache.h"
>  #include "dir.h"
> +#include "refs.h"
>  #include "string-list.h"
>  
>  static int inside_git_dir = -1;
> @@ -263,6 +264,15 @@ int get_common_dir_noenv(struct strbuf *sb, const char *gitdir)
>  	return ret;
>  }
>  
> +int ref_storage_backend_config(const char *var, const char *value, void *ptr)
> +{
> +	char **cdata = ptr;
> +
> +	if (!strcmp(var, "extensions.refstorage"))
> +		*cdata = xstrdup(value);
> +	return 0;
> +}
> +
>  /*
>   * Test if it looks like we're at a git directory.
>   * We want to see:
> @@ -390,6 +400,8 @@ static int check_repo_format(const char *var, const char *value, void *cb)
>  			;
>  		else if (!strcmp(ext, "preciousobjects"))
>  			repository_format_precious_objects = git_config_bool(var, value);
> +		else if (!strcmp(ext, "refstorage"))
> +			ref_storage_backend = xstrdup(value);
>  		else
>  			string_list_append(&unknown_extensions, ext);
>  	}
> diff --git a/t/t0001-init.sh b/t/t0001-init.sh
> index 295aa59..31c8279 100755
> --- a/t/t0001-init.sh
> +++ b/t/t0001-init.sh
> @@ -174,6 +174,31 @@ test_expect_success 'reinit' '
>  	test_i18ncmp again/empty again/err2
>  '
>  
> +test_expect_success 'init with bogus storage backend fails' '
> +
> +	(
> +		mkdir again2 &&
> +		cd again2 &&
> +		test_must_fail git init --ref-storage=test >out2 2>err2 &&
> +		test_i18ngrep "Unknown ref storage backend test" err2
> +	)
> +'
> +
> +test_expect_failure 'reinit with changed storage backend fails' '
> +
> +	(
> +		mkdir again3 &&
> +		cd again3 &&
> +		git init >out1 2>err1 &&
> +		git init --ref-storage=test >out2 2>err2
> +	) &&
> +	test_i18ngrep "Initialized empty" again3/out1 &&
> +	test_i18ngrep "Reinitialized existing" again3/out2 &&
> +	>again3/empty &&
> +	test_i18ncmp again3/empty again3/err1 &&
> +	test_i18ncmp again3/empty again3/err2
> +'
> +