Commit log linting not checking all PR commits

[llorllale]

This is due to an erroneous assumption: the linter would be run in the feature branch. The problem is that both rultor and travis run scripts after merging the feature and master branches together.

In this context, the --not master predicate passed to git log does not produce the expected output.

I thought about using git's --author filter but neither travis nor rultor expose the PR's author. (Regarding rultor, let's keep in mind that there are sometimes unicode decoding issues, so we'll keep gitlint disabled in rultor for now).

Since there are many dirty messages in our commit history, we should just lint all commit logs since a last known good revision. I would choose d0b2b05 but git log d0b2b05d977b43d705f89f1c286a4262b534c6b4.. includes many commits I did not expect and I don't know yet why it does that.

So for now git log --since="2019-01-21" produces an output that we can work on, so we'll use that.

[llorllale]

@llorllale fixed in ab8f142

[0crat]

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[0crat]

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