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>

2 files changed, 56 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.
diff --git a/testsuite/patch.tests b/testsuite/patch.tests
index 2759d2ad4..39205242c 100755
--- a/testsuite/patch.tests
+++ b/testsuite/patch.tests
@@ -242,6 +242,51 @@ patch: can't open 'dir2///file': No such file or directory
  zxc
 "
 
+testing "patch internal buffering bug?" \
+        'patch -p1 2>&1; echo $?; cat input' \
+"\
+patching file input
+0
+foo
+
+
+
+
+
+
+1
+2
+3
+
+bar
+" \
+"\
+foo
+
+
+
+
+
+
+
+bar
+" \
+"\
+--- a/input.orig
++++ b/input
+@@ -5,5 +5,8 @@ foo
+ 
+ 
+ 
++1
++2
++3
+ 
+ bar
+-- 
+2.9.2
+" \
+
 rm input.orig 2>/dev/null
 
 exit $FAILCOUNT