Subject: Re: [PATCH v4 4/6] config: correctly read worktree configs in submodules

From: Jonathan Nieder <[email-masked]>
Date: Mon, 31 Aug 2020 19:41:30 -0700

Hi,

Matheus Tavares wrote:

> One of the steps in do_git_config_sequence() is to load the
> worktree-specific config file. Although the function receives a git_dir
> string, it relies on git_pathdup(), which uses the_repository->git_dir,
> to make the path to the file. Furthermore, it also checks that
> extensions.worktreeConfig is set through the
> repository_format_worktree_config variable, which refers to
> the_repository only. Thus, when a submodule has worktree-specific
> settings, a command executed in the superproject that recurses into the
> submodule won't find the said settings.

I think the above goes out of order: it states the "how" before the
"what".  Instead, a commit message should lead with the problem the
change aims to solve.

Is the idea here that until this patch, we're only able to read
worktree config from a repository when extensions.worktreeConfig is
set in the_repository, meaning that

- when examining submodule config in a process where the_repository
  represents the superproject, we do not read the submodule's worktree
  config even if extensions.worktreeConfig is set in the submodule,
  unless the superproject has extensions.worktreeConfig set, and

- when examining submodule config in a process where the_repository
  represents the superproject, we *do* read the submodule's worktree
  config even if extensions.worktreeConfig is not set in the submodule,
  if the superproject has extensions.worktreeConfig set, and

?

That sounds like a serious problem indeed.  Thanks for fixing it.

> This will be especially important in the next patch: git-grep will learn
> to honor sparse checkouts and, when running with --recurse-submodules,
> the submodule's sparse checkout settings must be loaded. As these
> settings are stored in the config.worktree file, they would be ignored
> without this patch. So let's fix this by reading the right
> config.worktree file and extensions.worktreeConfig setting, based on the
> git_dir and commondir paths given to do_git_config_sequence(). Also
> add a test to avoid any regressions.

I see.  I'm not sure that's more important than other cases, but I
can understand if the problem was noticed in this circumstance. :)

> Signed-off-by: Matheus Tavares <[email-masked]>
> ---
>  config.c                   | 21 +++++++++---
>  t/helper/test-config.c     | 67 +++++++++++++++++++++++++++++++++-----
>  t/t2404-worktree-config.sh | 16 +++++++++
>  3 files changed, 91 insertions(+), 13 deletions(-)
> 
> diff --git a/config.c b/config.c
> index 8db9c77098..c2d56309dc 100644
> --- a/config.c
> +++ b/config.c
> @@ -1747,11 +1747,22 @@ static int do_git_config_sequence(const struct config_options *opts,
>  		ret += git_config_from_file(fn, repo_config, data);
>  
>  	current_parsing_scope = CONFIG_SCOPE_WORKTREE;
> -	if (!opts->ignore_worktree && repository_format_worktree_config) {
> +	if (!opts->ignore_worktree && repo_config && opts->git_dir) {

Can we eliminate the repository_format_worktree_config global to save
the next caller from the same problem?

> +		struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
> +		struct strbuf buf = STRBUF_INIT;
> +
> +		read_repository_format(&repo_fmt, repo_config);
> +
> +		if (!verify_repository_format(&repo_fmt, &buf) &&
> +		    repo_fmt.worktree_config) {

This undoes the caching the repository_format_worktree_config means to
do.  Can we cache the value in "struct repository" instead?  That way,
in the common case where we're reading the_repository, we wouldn't
experience a slowdown.

> -		char *path = git_pathdup("config.worktree");
> +			char *path = mkpathdup("%s/config.worktree", opts->git_dir);

Can this use a helper like repo_git_path or strbuf_repo_git_path
(preferably one using strbuf like the latter)?

[...]
> +		strbuf_release(&buf);
> +		clear_repository_format(&repo_fmt);
>  	}
>  
>  	current_parsing_scope = CONFIG_SCOPE_COMMAND;
> diff --git a/t/helper/test-config.c b/t/helper/test-config.c
> index 61da2574c5..284f83a921 100644
> --- a/t/helper/test-config.c
> +++ b/t/helper/test-config.c
> @@ -2,12 +2,19 @@
>  #include "cache.h"
>  #include "config.h"
>  #include "string-list.h"
> +#include "submodule-config.h"
>  
>  /*
>   * This program exposes the C API of the configuration mechanism
>   * as a set of simple commands in order to facilitate testing.
>   *
> - * Reads stdin and prints result of command to stdout:
> + * Usage: test-tool config [--submodule=<path>] <cmd> [<args>]
> + *
> + * If --submodule=<path> is given, <cmd> will operate on the submodule at the
> + * given <path>. This option is not valid for the commands: read_early_config,
> + * configset_get_value and configset_get_value_multi.

Nice!

[...]
> @@ -93,7 +102,18 @@ int cmd__config(int argc, const char **argv)
>  	if (argc == 0)
>  		goto print_usage_error;
>  
> +	if (skip_prefix(*argv, "--submodule=", &subrepo_path)) {
> +		argc--;
> +		argv++;
> +		if (argc == 0)
> +			goto print_usage_error;
> +	}

Can this use the parse_options API?

> +
>  	if (argc == 2 && !strcmp(argv[0], "read_early_config")) {
> +		if (subrepo_path) {
> +			fprintf(stderr, "Cannot use --submodule with read_early_config\n");
> +			return TC_USAGE_ERROR;

Should this use die() or BUG()?

> +		}
>  		read_early_config(early_config_cb, (void *)argv[1]);
>  		return TC_SUCCESS;
>  	}
> @@ -101,8 +121,23 @@ int cmd__config(int argc, const char **argv)
>  	setup_git_directory();
>  	git_configset_init(&cs);
>  
> +	if (subrepo_path) {
> +		const struct submodule *sub;
> +		struct repository *subrepo = xcalloc(1, sizeof(*repo));

nit: this could be scoped to cmd__config:

	struct repository subrepo = {0};

> +
> +		sub = submodule_from_path(the_repository, &null_oid, subrepo_path);
> +		if (!sub || repo_submodule_init(subrepo, the_repository, sub)) {
> +			fprintf(stderr, "Invalid argument to --submodule: '%s'\n",
> +				subrepo_path);
> +			free(subrepo);
> +			ret = TC_USAGE_ERROR;

Likewise: I think may want to use die() or BUG() (and likewise for other
USAGE_ERROR cases).

Thanks and hope that helps,
Jonathan