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Date:   Sat, 31 Dec 2016 01:40:53 -0500
From:   Jeff King <peff@peff.net>
To:     Michael Haggerty <mhagger@alum.mit.edu>
Cc:     Junio C Hamano <gitster@pobox.com>, git@vger.kernel.org,
        David Turner <novalis@novalis.org>
Subject: Re: [PATCH v3 20/23] try_remove_empty_parents(): don't trash
 argument contents
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On Sat, Dec 31, 2016 at 04:13:00AM +0100, Michael Haggerty wrote:

> It's bad manners and surprising and therefore error-prone.

Agreed.

I wondered while reading your earlier patch whether the
safe_create_leading_directories() function had the same problem, but it
carefully replaces the NUL it inserts.

> -static void try_remove_empty_parents(char *refname)
> +static void try_remove_empty_parents(const char *refname)
>  {
> +	struct strbuf buf = STRBUF_INIT;
>  	char *p, *q;
>  	int i;
> -	p = refname;
> +
> +	strbuf_addstr(&buf, refname);

I see here you just make a copy. I think it would be enough to do:

> @@ -2305,10 +2306,11 @@ static void try_remove_empty_parents(char *refname)
>  			q--;
>  		if (q == p)
>  			break;
> -		*q = '\0';
> -		if (rmdir(git_path("%s", refname)))
> +		strbuf_setlen(&buf, q - buf.buf);
> +		if (rmdir(git_path("%s", buf.buf)))
>  			break;

  *q = '\0';
  r = rmdir(git_path("%s", refname));
  *q = '/';

  if (r)
          break;

or something. But I doubt the single allocation is breaking the bank,
and it has the nice side effect that callers can pass in a const string
(I didn't check yet whether that enables further cleanups).

-Peff