grep: drop grep_buffer's "name" parameter

Before the grep_source interface existed, grep_buffer was
used by two types of callers:

  1. Ones which pulled a file into a buffer, and then wanted
     to supply the file's name for the output (i.e.,
     git grep).

  2. Ones which really just wanted to grep a buffer (i.e.,
     git log --grep).

Callers in set (1) should now be using grep_source. Callers
in set (2) always pass NULL for the "name" parameter of
grep_buffer. We can therefore get rid of this now-useless
parameter.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/grep.h b/grep.h
index e386ca4..8bf3001 100644
--- a/grep.h
+++ b/grep.h
@@ -127,7 +127,7 @@
 extern void append_header_grep_pattern(struct grep_opt *, enum grep_header_field, const char *);
 extern void compile_grep_patterns(struct grep_opt *opt);
 extern void free_grep_patterns(struct grep_opt *opt);
-extern int grep_buffer(struct grep_opt *opt, const char *name, char *buf, unsigned long size);
+extern int grep_buffer(struct grep_opt *opt, char *buf, unsigned long size);
 
 struct grep_source {
 	char *name;