Subject: Re: [RFC/PATCH v2 2/3] run-command: make sure hooks have always GIT_DIR

From: Junio C Hamano <[email-masked]>
Date: Wed, 23 Apr 2014 13:37:59 -0700

Felipe Contreras <[email-masked]> writes:

> Signed-off-by: Felipe Contreras <[email-masked]>

Why is this a good change?  From a zero-line log message, I cannot
even tell if this is trying to fix some problem, or trying to give
new capabilities to hooks.

How does it prevent existing hook scripts from suddenly start
misbehaving, where they do *not* expect to see an explicit GIT_DIR
pointing at the original repository hook gets run in exported into
their environment?  For example, one of my post-receive hooks in a
repository I push into records $cwd (which is the GIT_DIR of
receiving repository), chdir's to another repository and then
executes "git pull $cwd" from there, and that relies on the fact
that being at the top-level of that other repository without GIT_DIR
environment pointing at elsewhere but having .git directory in that
top-level repository is sufficient to kick the auto-discovery of the
repository that receives the "pull" in order to work correctly.

> ---
>  run-command.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/run-command.c b/run-command.c
> index 75abc47..8e188f6 100644
> --- a/run-command.c
> +++ b/run-command.c
> @@ -765,12 +765,29 @@ int run_hook_ve(const char *const *env, const char *name, va_list args)
>  	struct child_process hook;
>  	struct argv_array argv = ARGV_ARRAY_INIT;
>  	const char *p;
> -	int ret;
> +	const char **mod_env = NULL;
> +	int ret, i = 0;
> +	struct strbuf buf = STRBUF_INIT;
>  
>  	p = find_hook(name);
>  	if (!p)
>  		return 0;
>  
> +	if (!getenv(GIT_DIR_ENVIRONMENT)) {
> +		if (env)
> +			for (i = 0; env[i]; i++);
> +
> +		mod_env = xcalloc(i + 2, sizeof(*mod_env));
> +
> +		if (env)
> +			for (i = 0; env[i]; i++)
> +				mod_env[i] = env[i];
> +
> +		strbuf_addf(&buf, "GIT_DIR=%s", get_git_dir());
> +		mod_env[i++] = buf.buf;
> +		mod_env[i++] = NULL;
> +	}
> +
>  	argv_array_push(&argv, p);
>  
>  	while ((p = va_arg(args, const char *)))
> @@ -778,12 +795,15 @@ int run_hook_ve(const char *const *env, const char *name, va_list args)
>  
>  	memset(&hook, 0, sizeof(hook));
>  	hook.argv = argv.argv;
> -	hook.env = env;
> +	hook.env = mod_env ? mod_env : env;
>  	hook.no_stdin = 1;
>  	hook.stdout_to_stderr = 1;
>  
>  	ret = run_command(&hook);
>  	argv_array_clear(&argv);
> +	strbuf_release(&buf);
> +	free(mod_env);
> +
>  	return ret;
>  }