MAINT: Adds doit.db.db to gitignore

[thomasjpfan]

Reference issue

Follow up to #15959

What does this implement/fix?

I noticed that doit creates this db file and I think it should be ignored by git.

[tylerjereddy]

Interesting, on my machine I see .doit.db that is not being ignored--you're getting the repeated extension on your end? I guess we can add yours and mine.

I noticed that the one I see is also in the pydoit .gitginore proper: https://github.com/pydoit/doit/blob/master/.gitignore#L2

[thomasjpfan]

Yea I get .doit.db.db although it looks like the doit docs only mention .doit.db.

I updated the PR by adding .doit.db as well: fa56596 (#15999)

[schettino72]

doit internally uses stdlib dbm [1]. Which implementation (and extension applied) depends on the default implementation in your installation. Unfortunately the extension added (or not) to the files is inconsistent...

[1] https://docs.python.org/3/library/dbm.html

[tylerjereddy]

thanks!