Re: Bug in git submodule update --remote

[Atharva Raykar <raykar.ath@gmail.com>]

On 19-May-2021, at 20:11, Ben Avison <bavison@riscosopen.org> wrote:
> 
> On 19/05/2021 11:49, Atharva Raykar wrote:
>> If I understood you correctly, you'd prefer that the updating of the
>> submodule should be independent of the ref that is checked out in the
>> submodule's directory.
>> 
>> While I am not sure of the reason why the design of 'update
>> --remote' uses the remote-tracking branch of the submodule, I can
>> imagine adding a switch like 'submodule.<name>.remote' that defaults
>> to 'origin'. Then the behaviour could be changed such that it always 
>> pulls from the remote specified in that option.
>> 
>> This would help make the behaviour consistent in all the cases you 
>> mentioned, while also giving the option for a user to update the 
>> submodule from the remote of their choice (which may not be origin).
> 
> I like that solution. Although, I should note that if the user has set
> submodule.<name>.remote to something other than 'origin', they will need
> to ensure that submodule.<name>.branch is also set, or they will still
> hit the "Unable to find current <remote>/HEAD revision in submodule"
> error that I initially stumbled on.
> 
> How about an implementation like the following? I introduced a new "git
> submodule--helper" command rather than modify "print-default-remote" for
> a couple of reasons:
> 
> 1) "print-default-remote" is also used for "git submodule sync" (I'm not
> sure if we should change its behaviour too)
> 
> 2) "print-default-remote" needs to be executed from within the
> submodule, and takes no arguments, whereas I need to parse the
> superproject's .git/config so need to be executed from the superproject
> and take the submodule path as an argument
> 
> The two functions I added are heavily based on "git submodule--helper
> remote-branch". However:
> 
> * Unlike with the branch name, I don't fall back to using the name for
> the remote cached from when we read the .gitmodules file, if it isn't
> found in .git/config. It doesn't make sense to me for the .gitmodules
> file to include this information, as any new clones will only contain
> "origin" remotes anyway.
> 
> * I removed "struct strbuf sb" since I don't think it's used.
> 
> Ben

Thanks for this. I am quite new around here, and I will be working
on porting the whole of 'submodule update' to C in the coming months.

Since this would modify the behaviour of the update subcommand, I
have decided to CC my mentors (Christian and Shourya) who are more
qualified than me to comment on this proposal.

I personally feel that the current behaviour where the remote used
depends on how the submodule is checked out is odd, and I don't
mind addressing it while doing the conversion of this functionality.

> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index 9d505a6329..25ce3c8a1d 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -2444,6 +2444,41 @@ static int resolve_remote_submodule_branch(int argc, const char **argv,
> 	return 0;
> }
> 
> +static const char *remote_submodule_remote(const char *path)
> +{
> +	const struct submodule *sub;
> +	const char *remote = NULL;
> +	char *key;
> +
> +	sub = submodule_from_path(the_repository, &null_oid, path);
> +	if (!sub)
> +		return NULL;
> +
> +	key = xstrfmt("submodule.%s.remote", sub->name);
> +	repo_config_get_string_tmp(the_repository, key, &remote);
> +	free(key);
> +
> +	if (!remote)
> +		return "origin";
> +
> +	return remote;
> +}
> +
> +static int resolve_remote_submodule_remote(int argc, const char **argv,
> +		const char *prefix)
> +{
> +	const char *ret;
> +	if (argc != 2)
> +		die("submodule--helper remote-remote takes exactly one arguments, got %d", argc);
> +
> +	ret = remote_submodule_remote(argv[1]);
> +	if (!ret)
> +		die("submodule %s doesn't exist", argv[1]);
> +
> +	printf("%s", ret);
> +	return 0;
> +}
> +
> static int push_check(int argc, const char **argv, const char *prefix)
> {
> 	struct remote *remote;
> @@ -2770,6 +2805,7 @@ static struct cmd_struct commands[] = {
> 	{"deinit", module_deinit, 0},
> 	{"summary", module_summary, SUPPORT_SUPER_PREFIX},
> 	{"remote-branch", resolve_remote_submodule_branch, 0},
> +	{"remote-remote", resolve_remote_submodule_remote, 0},
> 	{"push-check", push_check, 0},
> 	{"absorb-git-dirs", absorb_git_dirs, SUPPORT_SUPER_PREFIX},
> 	{"is-active", is_active, 0},
> diff --git a/git-submodule.sh b/git-submodule.sh
> index eb90f18229..4d0df1cf5a 100755
> --- a/git-submodule.sh
> +++ b/git-submodule.sh
> @@ -577,7 +577,7 @@ cmd_update()
> 				fetch_in_submodule "$sm_path" $depth ||
> 				die "$(eval_gettext "Unable to fetch in submodule path '\$sm_path'")"
> 			fi
> -			remote_name=$(sanitize_submodule_env; cd "$sm_path" && git submodule--helper print-default-remote)
> +			remote_name=$(git submodule--helper remote-remote "$sm_path")
> 			sha1=$(sanitize_submodule_env; cd "$sm_path" &&
> 				git rev-parse --verify "${remote_name}/${branch}") ||
> 			die "$(eval_gettext "Unable to find current \${remote_name}/\${branch} revision in submodule path '\$sm_path'")"