Subject: Re: [PATCH 10/16] update submodules: is_submodule_checkout_safe

From: Brandon Williams <[email-masked]>
Date: Tue, 15 Nov 2016 16:06:21 -0800

On 11/15, Stefan Beller wrote:
> In later patches we introduce the options and flag for commands
> that modify the working directory, e.g. git-checkout.
> 
> This piece of code will answer the question:
> "Is it safe to change the submodule to this new state?"
> e.g. is it overwriting untracked files or are there local
> changes that would be overwritten?
> 
> Signed-off-by: Stefan Beller <[email-masked]>
> ---
>  submodule.c | 22 ++++++++++++++++++++++
>  submodule.h |  2 ++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/submodule.c b/submodule.c
> index 2773151..2149ef7 100644
> --- a/submodule.c
> +++ b/submodule.c
> @@ -1201,6 +1201,28 @@ int ok_to_remove_submodule(const char *path)
>  	return ok_to_remove;
>  }
>  
> +int is_submodule_checkout_safe(const char *path, const struct object_id *oid)
> +{
> +	struct child_process cp = CHILD_PROCESS_INIT;
> +
> +	if (!is_submodule_populated(path))
> +		/* The submodule is not populated, it's safe to check it out */
> +		/*
> +		 * TODO: When git learns to re-populate submodules, a check must be
> +		 * added here to assert that no local files will be overwritten.
> +		 */

When you mean local files do you mean in the situation where we want to
checkout a submodule at path 'foo' but there already exists a file at
path 'foo'?

> +		return 1;
> +
> +	argv_array_pushl(&cp.args, "read-tree", "-n", "-m", "HEAD",
> +			 sha1_to_hex(oid->hash), NULL);
> +
> +	prepare_submodule_repo_env(&cp.env_array);
> +	cp.git_cmd = 1;
> +	cp.no_stdin = 1;
> +	cp.dir = path;
> +	return run_command(&cp) == 0;
> +}
> +
>  static int find_first_merges(struct object_array *result, const char *path,
>  		struct commit *a, struct commit *b)
>  {
> diff --git a/submodule.h b/submodule.h
> index f01f87c..a7fa634 100644
> --- a/submodule.h
> +++ b/submodule.h
> @@ -74,6 +74,8 @@ extern unsigned is_submodule_modified(const char *path, int ignore_untracked);
>  extern int is_submodule_populated(const char *path);
>  extern int submodule_uses_gitfile(const char *path);
>  extern int ok_to_remove_submodule(const char *path);
> +extern int is_submodule_checkout_safe(const char *path,
> +				      const struct object_id *oid);
>  extern int merge_submodule(unsigned char result[20], const char *path,
>  			   const unsigned char base[20],
>  			   const unsigned char a[20],
> -- 
> 2.10.1.469.g00a8914
> 

-- 
Brandon Williams