xdiff: factor out is_func_rec()

Add a helper for checking if a given record is a function line.  It
frees callers from having to deal with the buffer arguments of
match_func_rec().

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

xdiff/xemit.c

@@ -121,6 +121,12 @@ static long match_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri,
 	return xecfg->find_func(rec, len, buf, sz, xecfg->find_func_priv);
 }
 
+static int is_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri)
+{
+	char dummy[1];
+	return match_func_rec(xdf, xecfg, ri, dummy, sizeof(dummy)) >= 0;
+}
+
 struct func_line {
 	long len;
 	char buf[80];
@@ -178,7 +184,6 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 
 			/* Appended chunk? */
 			if (i1 >= xe->xdf1.nrec) {
-				char dummy[1];
 				long i2 = xch->i2;
 
 				/*
@@ -186,8 +191,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 				 * a whole function was added.
 				 */
 				while (i2 < xe->xdf2.nrec) {
-					if (match_func_rec(&xe->xdf2, xecfg, i2,
-						dummy, sizeof(dummy)) >= 0)
+					if (is_func_rec(&xe->xdf2, xecfg, i2))
 						goto post_context_calculation;
 					i2++;
 				}