github fetch not working

[Gary Aitken]

Trying to work up a development port of ufraw, fetching from
   https://github.com/sergiomb2/ufraw.git
(or at least that's where I can get the source manually)
Going slowly, just trying to get the source fetched properly:

/!\ ufraw-devel-g20161113: Makefile warnings, please consider fixing /!\

Not validating first entry in CATEGORIES due to being outside of PORTSDIR.
Please ensure this is proper when committing.

===>  License GPLv2 accepted by the user
===>   ufraw-devel-g20161113 depends on file: /usr/local/sbin/pkg - found
=> sergiomb2-ufraw-g20161113_GH0.tar.gz doesn't seem to exist in ../../distfiles/ufraw-devel.
=> Attempting to fetch https://codeload.github.com/sergiomb2/ufraw/tar.gz/g20161113?dummy=/sergiomb2-ufraw-g20161113_GH0.tar.gz
fetch: https://codeload.github.com/sergiomb2/ufraw/tar.gz/g20161113?dummy=/sergiomb2-ufraw-g20161113_GH0.tar.gz: Not Found
=> Attempting to fetch http://distcache.FreeBSD.org/ports-distfiles/ufraw-devel/sergiomb2-ufraw-g20161113_GH0.tar.gz
fetch: http://distcache.FreeBSD.org/ports-distfiles/ufraw-devel/sergiomb2-ufraw-g20161113_GH0.tar.gz: Not Found
=> Couldn't fetch it - please try to retrieve this
=> port manually into ../../distfiles/ufraw-devel and try again.

It was my understanding that the USE_GITHUB target would somehow
magically clone the tree and build the requisite tarball, or unpack
the whole thing into distfiles.  Obviously I'm missing something.
Clues?

Makefile:
# $FreeBSD$

DISTDIR=        ../../distfiles
PORTNAME=       ufraw-devel
DISTVERSION=    g20161113
CATEGORIES=     graphics
#MASTER_SITES=  https://github.com/sergiomb2/ufraw.git

USE_GITHUB=     yes
GH_ACCOUNT=     sergiomb2
GH_PROJECT=     ufraw
#GH_TAGNAME=    g6d3259aa

DIST_SUBDIR=${PORTNAME}

MAINTAINER=     freebsd at dreamchaser.org
COMMENT=        Read and manipulate raw images from digital cameras
LICENSE=        GPLv2

.include <bsd.port.mk>

Thanks,
Gary