add working Portfile

MACPORTS.md

+(c) Stefan Countryman, 2019
+
+# Instructions on editing Portfiles for MacPorts
+
+- When updating version numbers for this module:
+  - Make sure that a tag exists in the git repository for the new version.
+  - Regenerate the rmd160 and sha256 hashes for the distribution file (the
+    tarball) using:
+    - `openssl dgst -rmd160 $DISTFILENAME`
+    - `openssl dgst -sha256 $DISTFILENAME`
+    - `ls -nl $DISTFILENAME | awk '{print $5}'`
+- Make sure that all dependencies are compatible with the python versions you
+  specify in python.versions.
+- Update the default python version to the newest stable version when possible
+- Note that the preferred homepage and master_site might change if the
+  maintainer changes/project switches hands
+
+# Testing a Portfile locally
+
+Instructions taken from
+[the MacPorts documentation](https://guide.macports.org/chunked/development.local-repositories.html).
+
+1. Since this is a python port, MacPorts expects to find the portfile in
+   `${ARBITRARY_PREFIX}/python/${name}/Portfile` where `${name}` is the name of the
+   port. So, to test, copy all your local Portfiles to directories following
+   this pattern. For example, with username `Stefan`, local port repository in
+   `~/dev/local-ports/`, and port name `py-gpstime`, you would copy the
+   portfile to `/Users/Stefan/dev/local-ports/python/py-gpstime/Portfile`.
+2. Insert the path to the local ports repository into
+   `/opt/local/etc/macports/sources.conf` by adding the line
+   `file:///Users/Stefan/dev/local-ports` (preferably ahead of the other sources
+   listed).
+3. Use portindex in the local repository's directory to create or update the
+   index of the ports in your local repository:
+   ```bash
+   cd ~/dev/local-ports
+   portindex
+   ```
+4. Try searching for and installing the new port as you ordinarily would, e.g.
+   `port search py-gpstime`.

Portfile

+# -*- coding: utf-8; mode: tcl; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- vim:fenc=utf-8:ft=tcl:et:sw=4:ts=4:sts=4
+
+PortSystem          1.0
+PortGroup           python 1.0
+
+name                py-gpstime
+version             0.3.2
+
+platforms           darwin
+supported_archs     noarch
+license             GPL-3
+maintainers         gmail.com:stefan.countryman
+
+python.rootname     gpstime
+
+description         GPS-aware datetime module with leap-second fetching \
+long_description    This package provides a gpstime package, including a \
+                    gpstime subclass of the built-in datetime class with the \
+                    addition of GPS access and conversion methods.  Leap \
+                    second data is provided by the ietf_leap_seconds module \
+                    that helps automatically maintain a local copy of the \
+                    IETF leap second list: \
+                    https://www.ietf.org/timezones/data/leap-seconds.list \
+                    A command-line GPS data conversion utility that uses the \
+                    gpstime module is also included.  It is a rough \
+                    work-alike to tconvert.
+                    
+homepage            https://git.ligo.org/jameson.rollins/${python.rootname}
+
+master_sites        https://git.ligo.org/jameson.rollins/${python.rootname}/-/archive/${version}/
+distname            ${python.rootname}-${version}
+extract.suffix      .tar.gz
+
+checksums           rmd160  d62957cd15570ce24e5e17d5fe6d587777698809 \
+                    sha256  b303807ba1e6a93f1ee1d47f36c014f2580348dd5045dd0cb28c1a59a0d700aa \
+                    size    23900
+
+python.versions         35 36
+
+python.default_version  36
+
+if {${name} ne ${subport}} {
+    livecheck.type  none
+} else {
+    livecheck.name  ${python.rootname}
+}