for-each-ref: extract helper functions out of grab_single_ref()

Extract two helper functions out of grab_single_ref(). Firstly,
new_refinfo() which is used to allocate memory for a new refinfo
structure and copy the objectname, refname and flag to it.
Secondly, match_name_as_path() which when given an array of patterns
and the refname checks if the refname matches any of the patterns
given while the pattern is a pathname, also supports wildcard
characters.

This is a preperatory patch for restructuring 'for-each-ref' and
eventually moving most of it to 'ref-filter' to provide the
functionality to similar commands via public API's.

Helped-by: Junio C Hamano <gitster@pobox.com>
Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/for-each-ref.c

@@ -850,6 +850,44 @@ struct grab_ref_cbdata {
 	int grab_cnt;
 };
 
+/*
+ * Return 1 if the refname matches one of the patterns, otherwise 0.
+ * A pattern can be path prefix (e.g. a refname "refs/heads/master"
+ * matches a pattern "refs/heads/") or a wildcard (e.g. the same ref
+ * matches "refs/heads/m*",too).
+ */
+static int match_name_as_path(const char **pattern, const char *refname)
+{
+	int namelen = strlen(refname);
+	for (; *pattern; pattern++) {
+		const char *p = *pattern;
+		int plen = strlen(p);
+
+		if ((plen <= namelen) &&
+		    !strncmp(refname, p, plen) &&
+		    (refname[plen] == '\0' ||
+		     refname[plen] == '/' ||
+		     p[plen-1] == '/'))
+			return 1;
+		if (!wildmatch(p, refname, WM_PATHNAME, NULL))
+			return 1;
+	}
+	return 0;
+}
+
+/* Allocate space for a new refinfo and copy the objectname and flag to it */
+static struct refinfo *new_refinfo(const char *refname,
+				   const unsigned char *objectname,
+				   int flag)
+{
+	struct refinfo *ref = xcalloc(1, sizeof(struct refinfo));
+	ref->refname = xstrdup(refname);
+	hashcpy(ref->objectname, objectname);
+	ref->flag = flag;
+
+	return ref;
+}
+
 /*
  * A call-back given to for_each_ref().  Filter refs and keep them for
  * later object processing.
@@ -866,35 +904,15 @@ static int grab_single_ref(const char *refname, const struct object_id *oid,
 		  return 0;
 	}
 
-	if (*cb->grab_pattern) {
-		const char **pattern;
-		int namelen = strlen(refname);
-		for (pattern = cb->grab_pattern; *pattern; pattern++) {
-			const char *p = *pattern;
-			int plen = strlen(p);
-
-			if ((plen <= namelen) &&
-			    !strncmp(refname, p, plen) &&
-			    (refname[plen] == '\0' ||
-			     refname[plen] == '/' ||
-			     p[plen-1] == '/'))
-				break;
-			if (!wildmatch(p, refname, WM_PATHNAME, NULL))
-				break;
-		}
-		if (!*pattern)
-			return 0;
-	}
+	if (*cb->grab_pattern && !match_name_as_path(cb->grab_pattern, refname))
+		return 0;
 
 	/*
 	 * We do not open the object yet; sort may only need refname
 	 * to do its job and the resulting list may yet to be pruned
 	 * by maxcount logic.
 	 */
-	ref = xcalloc(1, sizeof(*ref));
-	ref->refname = xstrdup(refname);
-	hashcpy(ref->objectname, oid->hash);
-	ref->flag = flag;
+	ref = new_refinfo(refname, oid->hash, flag);
 
 	cnt = cb->grab_cnt;
 	REALLOC_ARRAY(cb->grab_array, cnt + 1);