From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: [PATCHv2] submodule: Port resolve_relative_url from shell to C
Date: Thu, 17 Dec 2015 22:27:08 -0500
Message-ID: <20151218032708.GA8530@sigill.intra.peff.net>
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 <5673052F.7050000@kdbg.org>
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Cc: Stefan Beller <sbeller@google.com>, git@vger.kernel.org,
	gitster@pobox.com, jens.lehmann@web.de
To: Johannes Sixt <j6t@kdbg.org>
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On Thu, Dec 17, 2015 at 07:55:43PM +0100, Johannes Sixt wrote:

> -static int has_same_dir_prefix(const char *str, const char **out)
> +static int starts_with_dot_slash(const char *str)
>  {
> -#ifdef GIT_WINDOWS_NATIVE
> -	return skip_prefix(str, "./", out)
> -		|| skip_prefix(str, ".\\", out);
> -#else
> -	return skip_prefix(str, "./", out);
> -#endif
> +	return str[0] == '.' && is_dir_sep(str[1]);
>  }
>  
> -static int has_upper_dir_prefix(const char *str, const char **out)
> +static int starts_with_dot_dot_slash(const char *str)
>  {
> -#ifdef GIT_WINDOWS_NATIVE
> -	return skip_prefix(str, "../", out)
> -		|| skip_prefix(str, "..\\", out);
> -#else
> -	return skip_prefix(str, "../", out);
> -#endif
> +	return str[0] == '.' && str[1] == '.' && is_dir_sep(str[2]);
>  }

As the set of prefixes you are looking is probably bounded, it may not
be worth generalizing this. But I wondered if something like:

  /*
   * Like skip_prefix, but consider any "/" in the prefix as a
   * directory separator for the platform.
   */
  int skip_prefix_fs(const char *str, const char *prefix, const char **out)
  {
	while (1) {
		if (!*prefix) {
			*out = str;
			return 1;
		} else if (*prefix == '/') {
			if (!is_dir_sep(*str))
				return 0;
		} else {
			if (*str != *prefix)
				return 0;
		}
		str++;
		prefix++;
	}
  }

  ...
  /* works on all platforms! */
  if (skip_prefix_fs(foo, "./", &out))
	...

would be helpful. I don't know if there are other opportunities in the
code base that could make use of this. If it's just these two sites,
it's probably not worth it.

-Peff