hy/get_version.py

import os, subprocess, runpy

# Try to get and update the version.

os.chdir(os.path.split(os.path.abspath(__file__))[0])
VERSIONFILE = os.path.join("hy", "version.py")

if "HY_VERSION" in os.environ:
    __version__ = os.environ["HY_VERSION"]
else:
    try:
        __version__ = (subprocess.check_output
                       (["git", "describe", "--tags", "--dirty"])
                       .decode('ASCII').strip()
                       .replace('-', '+', 1).replace('-', '.'))
        with open(VERSIONFILE, "wt") as o:
            o.write("__version__ = {!r}\n".format(__version__))

    except (subprocess.CalledProcessError, OSError):
        if os.path.exists(VERSIONFILE):
            __version__ = runpy.run_path(VERSIONFILE)['__version__']
        else:
            __version__ = "unknown"