Throw Error when collectGitInfo fails

[ryfloyd]

I spent far too long to understand why my reports to Coveralls.io was not showing any branch info, commit message, etc. My app is built with Docker, and it was excluding .git folder in my .dockerignore file. This resulted with missing formdata POST to coveralls.io.

Easily fixed by just including .git folder to my Docker container.

[mattn]

Do you expect that update README.md?

[ryfloyd]

Perhaps a warning log if the directory is missing the .git?

[gdm85]

The python tool has the possibility to pass the git information via environment variables; that is also possible for the codecov official tool and in general it is a good practice to not bloat the Docker image with the .git directory.

@mattn I would like to submit a PR to add support for git information via environment variables; I would use these for reference: https://github.com/coveralls-clients/coveralls-python/blob/a5de3ba/coveralls/git.py#L101

After that I can also add a CLI flag -require-git=false which - when set to true - makes the tool fail; this way we can prevent the existing behaviour (an error is printed) but allow more strict behaviours for troubleshooting and integrations.

What do you think?

[gdm85]

Implemented in #188