Store author/committer date as DATETIME instead of VARCHAR

[brianwarner]

Per @sgoggins' request, this feature would alter the tables to store the committer and author dates in a DATETIME column instead of VARCHAR. The context of the original decision is that the date info comes in as text from git log, and there wasn't any reason to do it otherwise. So, basically, laziness on my part...

Sean now has a reason, so this issue will track the downstream consequences of storing this commit data as a DATETIME. At minimum, it will require:

• Changing the column definitions for data and cache tables in setup.py
• Adding a clause to the function update_db() in facade-worker.py so that existing instances are properly updated
• Making sure everything displays properly in the web and cli views
• A new major release.

There are a few ways to do this. One is to alter the analysis_data table in-place, and force a recreation of the data. Another way is to split this data out separately (this appears preferable, as it will come with other benefits, and is tracked in a different issue).

[chrisinmtown]

Please consider using TIMESTAMP in Mysql which represents a well defined point in time unambiguously just as the git log data does -- both include a timezone offset.

[brianwarner]

Thanks! Is there a reason to prefer this over DATETIME?

[chrisinmtown]

I tried to give my reasoning above. DATETIME is old, TIMESTAMP is an improvement, but with that said, still can cause confusion.

FWIW there are ENORMOUS discussions on this topic in stackoverflow. For example https://stackoverflow.com/questions/31761047/what-difference-between-the-date-time-datetime-and-timestamp-types/56138746