diff -up common/Makefile.common.patch-rediff common/Makefile.common
--- common/Makefile.common.patch-rediff	2008-09-30 14:19:22.000000000 +0200
+++ common/Makefile.common	2008-09-30 16:59:59.000000000 +0200
@@ -108,7 +108,12 @@ endif
 
 # this is used in make patch, maybe make clean eventually.
 # would be nicer to autodetermine from the spec file...
-RPM_BUILD_DIR ?= $(BUILDDIR)/$(NAME)-$(VERSION)
+# look for %setup -n SOURCE_DIR in .spec and use it instead of default if exists
+NAME_VER_DIR := $(shell sed -ne '/^%setup .*-n/{s/.*-n \([^ ]*\)/\1/;s/%{name}/$(NAME)/;s/%{version}/$(VERSION)/;p}' $(SPECFILE))
+ifndef NAME_VER_DIR
+NAME_VER_DIR := $(NAME)-$(VERSION)
+endif
+RPM_BUILD_DIR ?= $(BUILDDIR)/$(NAME_VER_DIR)
 
 ## for secondary arch only packages we cant build on the primary hub
 ## we need to go direct to the secondary arch hub
@@ -581,7 +586,7 @@ endif
 
 patch:
 	@if test -z "$(SUFFIX)"; then echo "Must specify SUFFIX=whatever" ; exit 1; fi
-	(cd $(RPM_BUILD_DIR)/.. && gendiff $(NAME)-$(VERSION) .$(SUFFIX) | $(FILTERDIFF)) > $(PATCHFILE) || true
+	(cd $(RPM_BUILD_DIR)/.. && gendiff $(NAME_VER_DIR) .$(SUFFIX) | $(FILTERDIFF)) > $(PATCHFILE) || true
 	@if ! test -s $(PATCHFILE); then echo "Patch is empty!"; exit 1; fi
 	@echo "Created $(PATCHFILE)"
 	@grep "$(PATCHFILE)" CVS/Entries >&/dev/null || cvs add -ko $(PATCHFILE) || true
@@ -594,7 +599,7 @@ rediff:
 	@if ! test -f "$(PATCHFILE)"; then echo "$(PATCHFILE) not found"; exit 1; fi
 	@mv -f $(PATCHFILE) $(PATCHFILE)\~
 	@sed '/^--- /,$$d' < $(PATCHFILE)\~ > $(PATCHFILE)
-	@(cd $(RPM_BUILD_DIR)/.. && gendiff $(NAME)-$(VERSION) .$(SUFFIX) | $(FILTERDIFF)) >> $(PATCHFILE) || true
+	@(cd $(RPM_BUILD_DIR)/.. && gendiff $(NAME_VER_DIR) .$(SUFFIX) | $(FILTERDIFF)) >> $(PATCHFILE) || true
 
 clog: $(SPECFILE)
 	@sed -n '/^%changelog/,/^$$/{/^%/d;/^$$/d;s/%%/%/g;p}' $(SPECFILE) | tee $@