Add version info to druid package and use it for CLI version output

[simonvanderveldt]

This uses https://pypi.org/project/setuptools-scm/ + https://pypi.org/project/setuptools-scm-git-archive/ which is a bit "magic", but from my testing this is the only way to get the version automatically with the following criteria:

• The only action necessary to update the version is git tag
• Release archives from GitHub should work and show the correct version
• During development it should be clear that a "development version" is being used. Ideally the shorthash + something like dev should be shown

Some output examples:

$ druid --version          
druid, version 0.1.2.dev17+g971de94
$ git tag -a 0.1.3 -m "thisisatest"
$ druid --version
druid, version 0.1.3
$ echo "foo" > test.txt
$ git add test.txt
$ druid --version
druid, version 0.1.4.dev0+g07eb4c8.d20191021

And when making a release archive (which is what GitHub does):

$ git tag -a 0.1.3 -m "thisisatest" 
$ git archive add-version-info | gzip > test.tgz
$ tar -axf test.tgz .git_archival.txt -O       
ref-names: HEAD -> add-version-info, tag: 0.1.3, origin/add-version-info

And when installing from this archive

$ pip install test.tgz
...
$ druid --version
druid, version 0.1.3

@csboling what do you think?

Fixes #29

[trentgill]

This looks good to me, and I don't mind the extra packages now that we're using an automated setup with pip. I can't really comment on the implementation, but it's at least terse and reads cleanly to the uninitiated (read: myself).

Perhaps you could add a section to the readme which describes the necessary steps to make a new release? I know it's going to be automated at some point, but would be good to document the current situation.

[simonvanderveldt]

Perhaps you could add a section to the readme which describes the necessary steps to make a new release? I know it's going to be automated at some point, but would be good to document the current situation.

Good point! I'll add that tomorrow.

[trentgill]

@simonvanderveldt lmk what I can do to test this out and then let's check it in!

[simonvanderveldt]

@trentgill I don't expect it to behave differently on different OSes but if you could give it a spin on Mac OS and Windows that would be nice (although @csboling might do that as well)

[trentgill]

Tested all my systems and it seems to be working well! Merging now.

[csboling]

I just learned like seven new things about pip and git from trying to understand how this works, awesome. Very tidy solution!