[PATCH] wt-status: use strncmp() for length-limited string comparison

["René Scharfe" <l.s.r@web.de>]

When a branch name is longer than four characters, memcmp() can read
past the end of the string literal "HEAD".  Use strncmp() instead, which
stops at the end of a string.  This fixes the following test failures
with AddressSanitizer:

t3203-branch-output.sh                           (Wstat: 256 Tests: 18 Failed: 4)
  Failed tests:  12, 15-17
  Non-zero exit status: 1
t3412-rebase-root.sh                             (Wstat: 256 Tests: 31 Failed: 3)
  Failed tests:  28-29, 31
  Non-zero exit status: 1
t3507-cherry-pick-conflict.sh                    (Wstat: 256 Tests: 31 Failed: 4)
  Failed tests:  14, 29-31
  Non-zero exit status: 1
t3510-cherry-pick-sequence.sh                    (Wstat: 256 Tests: 39 Failed: 14)
  Failed tests:  17, 22-26, 28-30, 34-35, 37-39
  Non-zero exit status: 1
t3420-rebase-autostash.sh                        (Wstat: 256 Tests: 28 Failed: 4)
  Failed tests:  24-27
  Non-zero exit status: 1
t3404-rebase-interactive.sh                      (Wstat: 256 Tests: 91 Failed: 57)
  Failed tests:  17, 19, 21-42, 44, 46-74, 77, 81-82
  Non-zero exit status: 1
t3900-i18n-commit.sh                             (Wstat: 256 Tests: 34 Failed: 1)
  Failed test:  34
  Non-zero exit status: 1
t5407-post-rewrite-hook.sh                       (Wstat: 256 Tests: 14 Failed: 6)
  Failed tests:  9-14
  Non-zero exit status: 1
t7001-mv.sh                                      (Wstat: 256 Tests: 46 Failed: 5)
  Failed tests:  39-43
  Non-zero exit status: 1
t7509-commit.sh                                  (Wstat: 256 Tests: 12 Failed: 2)
  Failed tests:  11-12
  Non-zero exit status: 1
t7512-status-help.sh                             (Wstat: 256 Tests: 39 Failed: 35)
  Failed tests:  5-39
  Non-zero exit status: 1
t6030-bisect-porcelain.sh                        (Wstat: 256 Tests: 70 Failed: 1)
  Failed test:  13
  Non-zero exit status: 1

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 wt-status.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/wt-status.c b/wt-status.c
index 435fc28..8dc281b 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -1319,7 +1319,7 @@ static int grab_1st_switch(unsigned char *osha1, unsigned char *nsha1,
 	hashcpy(cb->nsha1, nsha1);
 	for (end = target; *end && *end != '\n'; end++)
 		;
-	if (!memcmp(target, "HEAD", end - target)) {
+	if (!strncmp(target, "HEAD", end - target)) {
 		/* HEAD is relative. Resolve it to the right reflog entry. */
 		strbuf_addstr(&cb->buf,
 			      find_unique_abbrev(nsha1, DEFAULT_ABBREV));
-- 
2.6.3