see Packaging software with RPM
diff -uNr the_package/the_file \
the_package/the_file.new > the_file.patch
copy the patch file to /usr/src/redhat/SOURCES
The spec file has those lines:
After Sources:
Patch0: the_file.patch
After %setup, before %build
%patch -p1 To get your new version from the original file:patch slapd.conf.template \
../../slapd.conf.template.patch \
-o slapd.conf.template.new
Use patched files in RPMs