Merge branch 'np/delta' into next

* np/delta:
  replace adler32 with Rabin's polynomial in diff-delta

diff --cc Makefile
index 4416af9,38c980b..576067f
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -609,11 -609,8 +609,11 @@@ test-date$X: test-date.c date.o ctype.
        $(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) test-date.c date.o ctype.o
  
  test-delta$X: test-delta.c diff-delta.o patch-delta.o
-       $(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $^ -lz
+       $(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $^
  
 +test-dump-cache-tree$X: dump-cache-tree.o $(GITLIBS)
 +      $(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(LIBS)
 +
  check:
        for i in *.c; do sparse $(ALL_CFLAGS) $(SPARSE_FLAGS) $$i || exit; done