Configuration option to define wether to follows GNU sed's behaviour

or the posix standard.
Put the cleanup code back the way it was.

testsuite/sed/sed-append-next-line

@@ -1,4 +1,6 @@
-busybox sed -n 'N;p'>output <<EOF
+# XFAIL
+# This will fail if CONFIG_FEATURE_SED_GNU_COMPATABILITY is defined
+busybox sed 'N;p'>output <<EOF
 a
 b
 c
@@ -6,4 +8,7 @@ EOF
 cmp -s output - <<EOF
 a
 b
+a
+b
+c
 EOF

testsuite/sed/sed-append-next-line-gnu

@@ -0,0 +1,14 @@
+# FEATURE: CONFIG_FEATURE_SED_GNU_COMPATABILITY
+busybox sed 'N;p'>output <<EOF
+a
+b
+c
+EOF
+cmp -s output - <<EOF
+a
+b
+a
+b
+c
+
+EOF