patch: fix -N regression

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

editors/patch.c

@@ -12,7 +12,6 @@
  * TODO:
  * -b backup
  * -l treat all whitespace as a single space
- * -N ignore already applied
  * -d chdir first
  * -D define wrap #ifdef and #ifndef around changes
  * -o outfile output here instead of in place
@@ -244,14 +243,12 @@ struct globals {
 } while (0)
 
 
-//bbox had: "p:i:RN"
 #define FLAG_STR "Rup:i:Nx"
 /* FLAG_REVERSE must be == 1! Code uses this fact. */
 #define FLAG_REVERSE (1 << 0)
 #define FLAG_u       (1 << 1)
 #define FLAG_PATHLEN (1 << 2)
 #define FLAG_INPUT   (1 << 3)
-// -N: not supported yet
 #define FLAG_IGNORE  (1 << 4)
 //non-standard:
 #define FLAG_DEBUG   (1 << 5)
@@ -314,6 +311,10 @@ static int apply_one_hunk(void)
 {
 	struct double_list *plist, *buf = NULL, *check;
 	int matcheof = 0, reverse = option_mask32 & FLAG_REVERSE, backwarn = 0;
+	/* Do we try "dummy" revert to check whether
+	 * to silently skip this hunk? Used to implement -N.
+	 */
+	int dummy_revert = 0;
 
 	// Break doubly linked list so we can use singly linked traversal function.
 	TT.current_hunk->prev->next = NULL;
@@ -343,9 +344,14 @@ static int apply_one_hunk(void)
 		while (plist && *plist->data == "+-"[reverse]) {
 			if (data && !strcmp(data, plist->data+1)) {
 				if (!backwarn) {
+					backwarn++;
+					if (option_mask32 & FLAG_IGNORE) {
+						dummy_revert = 1;
+						reverse ^= 1;
+						continue;
+					}
 					fdprintf(2,"Possibly reversed hunk %d at %ld\n",
 						TT.hunknum, TT.linenum);
-					backwarn++;
 				}
 			}
 			plist = plist->next;
@@ -409,7 +415,7 @@ static int apply_one_hunk(void)
 	}
 out:
 	// We have a match.  Emit changed data.
-	TT.state = "-+"[reverse];
+	TT.state = "-+"[reverse ^ dummy_revert];
 	llist_free(TT.current_hunk, do_line);
 	TT.current_hunk = NULL;
 	TT.state = 1;