patch: fix matching failure

Fix matching failure when plist is advanced while checking for buffered
lines - the lines in the hunk that are about to be added should be
skipped when checking for matching context.

Also add a valid test case that fails with current busybox and is fixed
by the change.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/editors/patch.c b/editors/patch.c
index 4ee9339a7..ea1fc0974 100644
--- a/editors/patch.c
+++ b/editors/patch.c
@@ -290,6 +290,17 @@ static int apply_one_hunk(void)
                 // out of buffer.
 
                 for (;;) {
+                        while (plist && *plist->data == "+-"[reverse]) {
+                                if (!strcmp(check->data, plist->data+1) &&
+                                    !backwarn) {
+                                        backwarn = TT.linenum;
+                                        if (option_mask32 & FLAG_IGNORE) {
+                                                dummy_revert = 1;
+                                                reverse ^= 1;
+                                        }
+                                }
+                                plist = plist->next;
+                        }
                         if (!plist || strcmp(check->data, plist->data+1)) {
                                 // Match failed.  Write out first line of buffered data and
                                 // recheck remaining buffered data for a new match.