patching PKGBUILD is broken

[bartoszek]

Before patching a PKGBUILD the patch file was added to PKGBUILD as one of sources which breaks the build script.
PKGBUILD : gpx-git
PKGBUILD.patch : http://pastebin.com/PPiY9kXC
/etc/customizepkg.d/gpx-git : patch#pkgbuild#PKGBUILD.patch
customizepkg output : http://pastebin.com/HG68dSS5

As a solution i can think off putting the modify_file before adding new files from ${CFGDIR}/${package} folder and marking PKGBUILD.patch in modify_file to be ignore in patch including function