pickaxe: count regex matches only once

When --pickaxe-regex is used, forward past the end of matches instead of
advancing to the byte after their start.  This way matches count only
once, even if the regular expression matches their tail -- like in the
fixed-string fork of the code.

E.g.: /.*/ used to count the number of bytes instead of the number of
lines.  /aa/ resulted in a count of two in "aaa" instead of one.

Also document the fact that regexec() needs a NUL-terminated string as
its second argument by adding an assert().

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index 574b3e8..d0ef839 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -25,10 +25,12 @@ static unsigned int contains(struct diff_filespec *one,
 		regmatch_t regmatch;
 		int flags = 0;
 
+		assert(data[sz] == '\0');
 		while (*data && !regexec(regexp, data, 1, &regmatch, flags)) {
 			flags |= REG_NOTBOL;
-			data += regmatch.rm_so;
-			if (*data) data++;
+			data += regmatch.rm_eo;
+			if (*data && regmatch.rm_so == regmatch.rm_eo)
+				data++;
 			cnt++;
 		}