Index: head/tools/build/depend-cleanup.sh
===================================================================
--- head/tools/build/depend-cleanup.sh	(revision 364801)
+++ head/tools/build/depend-cleanup.sh	(revision 364802)
@@ -1,45 +1,53 @@
 #!/bin/sh
 #
 # $FreeBSD$
 #
 # Our current make(1)-based approach to dependency tracking cannot cope with
 # certain source tree changes, including:
 # - removing source files
 # - replacing generated files with files committed to the tree
 # - changing file extensions (e.g. a C source file rewritten in C++)
 #
 # We handle those cases here in an ad-hoc fashion by looking for the known-
 # bad case in the main .depend file, and if found deleting all of the related
 # .depend files (including for example the lib32 version).
 #
 # These tests increase the build time (albeit by a small amount), so they
 # should be removed once enough time has passed and it is extremely unlikely
 # anyone would try a NO_CLEAN build against an object tree from before the
 # related change.  One year should be sufficient.
 
 OBJTOP=$1
 if [ ! -d "$OBJTOP" ]; then
 	echo "usage: $(basename $0) objtop" >&2
 	exit 1
 fi
 
 # $1 directory
 # $2 source filename w/o extension
 # $3 source extension
 clean_dep()
 {
 	if [ -e "$OBJTOP"/$1/.depend.$2.pico ] && \
 	    egrep -qw "$2\.$3" "$OBJTOP"/$1/.depend.$2.pico; then \
 		echo "Removing stale dependencies for $2.$3"; \
 		rm -f "$OBJTOP"/$1/.depend.$2.* \
 		    "$OBJTOP"/obj-lib32/$1/.depend.$2.*
 	fi
 }
 
 # Date      Rev      Description
 # 20190916  r352703  shm_open syscall reimplemented in C
 clean_dep lib/libc   shm_open S
 # 20200310  r358851  rename of openmp's ittnotify_static.c to .cpp
 clean_dep lib/libomp ittnotify_static c
 # 20200414  r359930  closefrom
 clean_dep lib/libc   closefrom S
+
+# 20200826  r364746  OpenZFS merge, apply a big hammer (remove whole tree)
+if [ -e "$OBJTOP"/cddl/lib/libzfs/.depend.libzfs_changelist.o ] && \
+    egrep -qw "cddl/contrib/opensolaris/lib/libzfs/common/libzfs_changelist.c" \
+    "$OBJTOP"/cddl/lib/libzfs/.depend.libzfs_changelist.o; then
+	echo "Removing old ZFS tree"
+	rm -rf "$OBJTOP"/cddl "$OBJTOP"/obj-lib32/cddl
+fi