Re: [PATCH v2 1/1] submodule--helper: fix incorrect newlines in an error message

> A refactoring[1] done as part of the recent conversion of
> 'git submodule add' to builtin, changed the error message
> shown when a Git directory already exists locally for a submodule
> name. Before the refactoring, the error used to appear like so:
>
>   --- START OF OUTPUT ---
>   $ git submodule add ../sub/ subm
>   A git directory for 'subm' is found locally with remote(s):
>     origin        /me/git-repos-for-test/sub
>   If you want to reuse this local git directory instead of cloning again from
>     /me/git-repos-for-test/sub
>   use the '--force' option. If the local git directory is not the correct repo
>   or you are unsure what this means choose another name with the '--name' option.
>   ---  END OF OUTPUT  ---
>
> After the refactoring the error started appearing like so:
>
>   --- START OF OUTPUT ---
>   $ git submodule add ../sub/ subm
>   A git directory for 'subm' is found locally with remote(s):  origin     /me/git-repos-for-test/sub
>   fatal: If you want to reuse this local git directory instead of cloning again from
>   /me/git-repos-for-test/sub
>   use the '--force' option. If the local git directory is not the correct repo
>   or if you are unsure what this means, choose another name with the '--name' option.
>
>   ---  END OF OUTPUT  ---
>
> As one could observe the remote information is printed along with the
> first line rather than on its own line. Also, there's an additional
> newline following output.
>
> Make the error message consistent with the error message that used to be
> printed before the refactoring.
>
> This also moves the 'fatal:' prefix that appears in the middle of the
> error message to the first line as it would more appropriate to have
> it in the first line. The output after the change would look like:
>
>   --- START OF OUTPUT ---
>   $ git submodule add ../sub/ subm
>   fatal: A git directory for 'subm' is found locally with remote(s):
>     origin        /me/git-repos-for-test/sub
>   If you want to reuse this local git directory instead of cloning again from
>     /me/git-repos-for-test/sub
>   use the '--force' option. If the local git directory is not the correct repo
>   or you are unsure what this means choose another name with the '--name' option.
>   ---  END OF OUTPUT  ---
>
> [1]: https://lore.kernel.org/git/20210710074801.19917-5-raykar.ath@gmail.com/#t
>
> Signed-off-by: Kaartic Sivaraam <kaartic.sivaraam@gmail.com>
> ---
>  builtin/submodule--helper.c | 36 ++++++++++++++++++++++--------------
>  1 file changed, 22 insertions(+), 14 deletions(-)
>
> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index 414fcb63ea..236da214c6 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -2775,7 +2775,7 @@ struct add_data {
>  };
>  #define ADD_DATA_INIT { .depth = -1 }
>
> -static void show_fetch_remotes(FILE *output, const char *sm_name, const char *git_dir_path)
> +static void show_fetch_remotes(struct strbuf *msg, const char *sm_name, const char *git_dir_path)

>  {
>  	struct child_process cp_remote = CHILD_PROCESS_INIT;
>  	struct strbuf sb_remote_out = STRBUF_INIT;
> @@ -2791,7 +2791,7 @@ static void show_fetch_remotes(FILE *output, const char *sm_name, const char *gi
>  		while ((next_line = strchr(line, '\n')) != NULL) {
>  			size_t len = next_line - line;
>  			if (strip_suffix_mem(line, &len, " (fetch)"))
> -				fprintf(output, "  %.*s\n", (int)len, line);
> +				strbuf_addf(msg, "  %.*s\n", (int)len, line);
>  			line = next_line + 1;
>  		}
>  	}
> @@ -2823,20 +2823,28 @@ static int add_submodule(const struct add_data *add_data)
>
>  		if (is_directory(submod_gitdir_path)) {
>  			if (!add_data->force) {
> -				fprintf(stderr, _("A git directory for '%s' is found "
> -						  "locally with remote(s):"),
> -					add_data->sm_name);
> -				show_fetch_remotes(stderr, add_data->sm_name,
> +				struct strbuf msg = STRBUF_INIT;
> +				char *die_msg;
> +
> +				strbuf_addf(&msg, _("A git directory for '%s' is found "
> +						    "locally with remote(s):\n"),
> +					    add_data->sm_name);
> +
> +				show_fetch_remotes(&msg, add_data->sm_name,
>  						   submod_gitdir_path);
>  				free(submod_gitdir_path);
> -				die(_("If you want to reuse this local git "
> -				      "directory instead of cloning again from\n"
> -				      "  %s\n"
> -				      "use the '--force' option. If the local git "
> -				      "directory is not the correct repo\n"
> -				      "or if you are unsure what this means, choose "
> -				      "another name with the '--name' option.\n"),
> -				    add_data->realrepo);
> +
> +				strbuf_addf(&msg, _("If you want to reuse this local git "
> +						    "directory instead of cloning again from\n"
> +						    "  %s\n"
> +						    "use the '--force' option. If the local git "
> +						    "directory is not the correct repo\n"
> +						    "or you are unsure what this means choose "
> +						    "another name with the '--name' option."),
> +					    add_data->realrepo);
> +
> +				die_msg = strbuf_detach(&msg, NULL);
> +				die("%s", die_msg);
>  			} else {
>  				printf(_("Reactivating local git directory for "
>  					 "submodule '%s'\n"), add_data->sm_name);