grep: factor out create_grep_pat()

Add create_grep_pat(), a shared helper for all grep pattern allocation
and initialization needs.

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

grep.c

@@ -3,15 +3,26 @@
 #include "userdiff.h"
 #include "xdiff-interface.h"
 
-void append_header_grep_pattern(struct grep_opt *opt, enum grep_header_field field, const char *pat)
+static struct grep_pat *create_grep_pat(const char *pat, size_t patlen,
+					const char *origin, int no,
+					enum grep_pat_token t,
+					enum grep_header_field field)
 {
 	struct grep_pat *p = xcalloc(1, sizeof(*p));
 	p->pattern = pat;
-	p->patternlen = strlen(pat);
-	p->origin = "header";
-	p->no = 0;
-	p->token = GREP_PATTERN_HEAD;
+	p->patternlen = patlen;
+	p->origin = origin;
+	p->no = no;
+	p->token = t;
 	p->field = field;
+	return p;
+}
+
+void append_header_grep_pattern(struct grep_opt *opt,
+				enum grep_header_field field, const char *pat)
+{
+	struct grep_pat *p = create_grep_pat(pat, strlen(pat), "header", 0,
+					     GREP_PATTERN_HEAD, field);
 	*opt->header_tail = p;
 	opt->header_tail = &p->next;
 	p->next = NULL;
@@ -26,12 +37,7 @@ void append_grep_pattern(struct grep_opt *opt, const char *pat,
 void append_grep_pat(struct grep_opt *opt, const char *pat, size_t patlen,
 		     const char *origin, int no, enum grep_pat_token t)
 {
-	struct grep_pat *p = xcalloc(1, sizeof(*p));
-	p->pattern = pat;
-	p->patternlen = patlen;
-	p->origin = origin;
-	p->no = no;
-	p->token = t;
+	struct grep_pat *p = create_grep_pat(pat, patlen, origin, no, t, 0);
 	*opt->pattern_tail = p;
 	opt->pattern_tail = &p->next;
 	p->next = NULL;