When doing operations on hunks, vim needs to recalculate hunk headers

[mcepl]

If I have these hunks:

index: python-2.6.7/makefile.pre.in
===================================================================
--- python-2.6.7.orig/makefile.pre.in	2012-02-08 18:42:19.000000000 +0100
+++ python-2.6.7/makefile.pre.in	2012-02-08 18:42:58.000000000 +0100
@@ -75,6 +75,8 @@
 
 # machine-dependent subdirectories
 machdep=	@machdep@
+lib=		@lib@
+arch=		@arch@
 
 # install prefix for architecture-independent files
 prefix=		@prefix@
@@ -509,6 +511,7 @@
 		-dexec_prefix='"$(exec_prefix)"' \
 		-dversion='"$(version)"' \
 		-dvpath='"$(vpath)"' \
+		-darch='"$(arch)"' -dlib='"$(lib)"' \
 		-o $@ $(srcdir)/modules/getpath.c
 
 modules/python.o: $(srcdir)/modules/python.c
@@ -540,7 +543,7 @@
 Python/compile.o Python/symtable.o: $(GRAMMAR_H) $(AST_H)
 
 Python/getplatform.o: $(srcdir)/Python/getplatform.c
-		$(CC) -c $(PY_CFLAGS) -DPLATFORM='"$(MACHDEP)"' -o $@ $(srcdir)/Python/getplatform.c
+		$(CC) -c $(PY_CFLAGS) -DPLATFORM='"linux2"' -DARCH='"$(ARCH)"' -DLIB='"$(LIB)"' -o $@ $(srcdir)/Python/getplatform.c
 
 Python/importdl.o: $(srcdir)/Python/importdl.c
 		$(CC) -c $(PY_CFLAGS) -I$(DLINCLDIR) -o $@ $(srcdir)/Python/importdl.c

Then the first one actually adds two lines, so I would expect that header of the second hunk after deleting the first one (didh) would change to @@ -509,6 +509,7 @@. It doesn't, it still stays the same. See https://gitlab.com/mcepl/vim-diff_navigator for the illustration, how it could be done. Not sure how to do it with vim text objects.