Make it possible to build from tarball again

[shibumi]

Hi,
I think @ArchangeGabriel already came up with this bug:

Traceback (most recent call last):
  File "setup.py", line 3, in <module>
    setup(
  File "/usr/lib/python3.8/site-packages/setuptools/__init__.py", line 145, in setup
    return distutils.core.setup(**attrs)
  File "/usr/lib/python3.8/distutils/core.py", line 108, in setup
    _setup_distribution = dist = klass(attrs)
  File "/usr/lib/python3.8/site-packages/setuptools/dist.py", line 446, in __init__
    _Distribution.__init__(self, {
  File "/usr/lib/python3.8/distutils/dist.py", line 292, in __init__
    self.finalize_options()
  File "/usr/lib/python3.8/site-packages/setuptools/dist.py", line 735, in finalize_options
    ep.load()(self, ep.name, value)
  File "/build/whipper/src/whipper-0.9.0/.eggs/setuptools_scm-3.3.3-py3.8.egg/setuptools_scm/integration.py", line 17, in version_keyword
    dist.metadata.version = get_version(**value)
  File "/build/whipper/src/whipper-0.9.0/.eggs/setuptools_scm-3.3.3-py3.8.egg/setuptools_scm/__init__.py", line 150, in get_version
    parsed_version = _do_parse(config)
  File "/build/whipper/src/whipper-0.9.0/.eggs/setuptools_scm-3.3.3-py3.8.egg/setuptools_scm/__init__.py", line 105, in _do_parse
    raise LookupError(
LookupError: setuptools-scm was unable to detect version for '/build/whipper/src/whipper-0.9.0'.

This can be fixed via cloning whipper from repository, I know.
But I would like to address this problem in this issue, because...

1. It makes your tarball basically useless
2. It undermines security, as a sha512 checksum for a tarball is much stronger than the usual used git hashes for commit or tags. (despite this, I still think you should sign your releases with a GPG key :) )

[shibumi]

As far as I see a solution for this issue:

You could add a PKG-INFO file to your repository. That way distributions would be able to build it from the tarball again.

[shibumi]

Hi I've found a way to mitigate this error:

echo "Version: 0.9.0" > PKG-INFO
Then everything works fine... but would be still cool if you could provide such a PKG-INFO file.

[JoeLametta]

This issue still needs to be addressed but in the meantime a (cleaner?) workaround (suggested by @mruszczyk) would be using the SETUPTOOLS_SCM_PRETEND_VERSION environment variable directly. More details HERE.

@jpalus You may be interested in this discussion.

Cheers,
Joe

[JoeLametta]

Hi I've found a way to mitigate this error:

echo "Version: 0.9.0" > PKG-INFO
Then everything works fine... but would be still cool if you could provide such a PKG-INFO file.

Maybe we could solve this issue providing such a file only in (future) tagged versions.