Subject: Re: [PATCH 2/8] repository, setup: introduce the_cwd

From: Junio C Hamano <[email-masked]>
Date: Sun, 21 Nov 2021 00:00:22 -0800

"Elijah Newren via GitGitGadget" <[email-masked]> writes:

> From: Elijah Newren <[email-masked]>
>
> Removing the current working directory causes all subsequent git
> commands (and likely a number of non-git commands) run from that
> directory to get confused and fail with a message about being unable to
> read the current working directory.  That confuses end users,
> particularly since the command they get the error from is not the one
> that caused the problem; the problem came from the side-effect of some
> previous command.
>
> We would like to avoid removing the current working directory; towards
> this end, introduce a new the_cwd variable that tracks the current
> working directory.  Subsequent commits will make use of this new
> variable.

Maybe a stupid question, but how is this different from doing getcwd()
and storing it away to the_cwd, or adding a check to see if the
directory we are about to rmdir() is the cwd, next to the existing
check that we do to see if that directory has some untracked files?

I am wondering how we are going to make sure that the_cwd is always
set to, and maintained to be, the correct value, even in the future
when these code paths change.  I also wonder if it might be safer to
learn what the value of cwd is very near the place where it will
become needed (i.e. the callsites of such rmdir() of a directory
inside working tree), instead of caching.

> Signed-off-by: Elijah Newren <[email-masked]>
> ---
>  repository.c | 1 +
>  repository.h | 1 +
>  setup.c      | 2 ++
>  3 files changed, 4 insertions(+)
>
> diff --git a/repository.c b/repository.c
> index c5b90ba93ea..69a106c553c 100644
> --- a/repository.c
> +++ b/repository.c
> @@ -17,6 +17,7 @@
>  static struct repository the_repo;
>  struct repository *the_repository;
>  struct index_state the_index;
> +char *the_cwd;
>  
>  void initialize_the_repository(void)
>  {
> diff --git a/repository.h b/repository.h
> index a057653981c..45de85d18ef 100644
> --- a/repository.h
> +++ b/repository.h
> @@ -147,6 +147,7 @@ struct repository {
>  };
>  
>  extern struct repository *the_repository;
> +extern char *the_cwd;
>  
>  /*
>   * Define a custom repository layout. Any field can be NULL, which
> diff --git a/setup.c b/setup.c
> index 347d7181ae9..4466fa55af3 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -887,6 +887,7 @@ static const char *setup_explicit_git_dir(const char *gitdirenv,
>  		set_git_dir(gitdirenv, 1);
>  		if (chdir(worktree))
>  			die_errno(_("cannot chdir to '%s'"), worktree);
> +		the_cwd = xstrdup(cwd->buf + offset);
>  		strbuf_addch(cwd, '/');
>  		free(gitfile);
>  		return cwd->buf + offset;
> @@ -940,6 +941,7 @@ static const char *setup_discovered_git_dir(const char *gitdir,
>  	/* Make "offset" point past the '/' (already the case for root dirs) */
>  	if (offset != offset_1st_component(cwd->buf))
>  		offset++;
> +	the_cwd = xstrdup(cwd->buf + offset);
>  	/* Add a '/' at the end */
>  	strbuf_addch(cwd, '/');
>  	return cwd->buf + offset;