Change exit code when no namespaces were linted and caching is enabled

[kjothen]

No longer consider No namespaces linted. as a warning if :only-modified true and the .eastwood file contains a valid timestamp.

Linting a large monorepo is time-consuming in CI builds. This can be mitigated by caching the .eastwood file between runs on the same branch. However, eastwood returns a non-zero exit code when no namespaces were linted, which is problematic. Rather than ignore the error code and continue the build, it would be better to return a zero error code in this circumstance.

Fixes: #454

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Before submitting the PR make sure the following things have been done (and denote this by checking the relevant checkboxes):

• [x] You've updated the changelog (if adding/changing user-visible functionality)
• [ ] You've updated the readme (if eg adding a new linter)

Thanks!

[kjothen]

Yeah, 3 mins is very manageable, but I remember when it was < 1 min in our early days, so it's crept up on us for sure! I made the changes you suggested, and thanks again.

[vemv]

Thanks to you!

I've tagged 1.4.3 - a release should be generated in < 1h.