From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 1 Nov 2016 19:58:49 +0000 (-0700)
Subject: Merge branch 'jk/no-looking-at-dotgit-outside-repo'
X-Git-Tag: v2.11.0-rc1~13
X-Git-Url: https://git.lorimer.id.au/gitweb.git/diff_plain/e828d33316925a50ed88e83b840daef2f98b4171?ds=inline;hp=-c

Merge branch 'jk/no-looking-at-dotgit-outside-repo'

A small code cleanup.

* jk/no-looking-at-dotgit-outside-repo:
sha1_name: make wraparound of the index into ring-buffer explicit
---

e828d33316925a50ed88e83b840daef2f98b4171
diff --combined sha1_name.c
index 06409a3845,45aa26b322..73a915ff1b
--- a/sha1_name.c
+++ b/sha1_name.c
@@@ -448,46 -448,10 +448,46 @@@ int for_each_abbrev(const char *prefix
  	return ret;
  }
  
 +/*
 + * Return the slot of the most-significant bit set in "val". There are various
 + * ways to do this quickly with fls() or __builtin_clzl(), but speed is
 + * probably not a big deal here.
 + */
 +static unsigned msb(unsigned long val)
 +{
 +	unsigned r = 0;
 +	while (val >>= 1)
 +		r++;
 +	return r;
 +}
 +
  int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
  {
  	int status, exists;
  
 +	if (len < 0) {
 +		unsigned long count = approximate_object_count();
 +		/*
 +		 * Add one because the MSB only tells us the highest bit set,
 +		 * not including the value of all the _other_ bits (so "15"
 +		 * is only one off of 2^4, but the MSB is the 3rd bit.
 +		 */
 +		len = msb(count) + 1;
 +		/*
 +		 * We now know we have on the order of 2^len objects, which
 +		 * expects a collision at 2^(len/2). But we also care about hex
 +		 * chars, not bits, and there are 4 bits per hex. So all
 +		 * together we need to divide by 2; but we also want to round
 +		 * odd numbers up, hence adding one before dividing.
 +		 */
 +		len = (len + 1) / 2;
 +		/*
 +		 * For very small repos, we stick with our regular fallback.
 +		 */
 +		if (len < FALLBACK_DEFAULT_ABBREV)
 +			len = FALLBACK_DEFAULT_ABBREV;
 +	}
 +
  	sha1_to_hex_r(hex, sha1);
  	if (len == 40 || !len)
  		return 40;
@@@ -510,7 -474,8 +510,8 @@@ const char *find_unique_abbrev(const un
  {
  	static int bufno;
  	static char hexbuffer[4][GIT_SHA1_HEXSZ + 1];
- 	char *hex = hexbuffer[3 & ++bufno];
+ 	char *hex = hexbuffer[bufno];
+ 	bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
  	find_unique_abbrev_r(hex, sha1, len);
  	return hex;
  }