Support for generating multiple output formats from single test run

[coderpatros]

The back story to this is that I use VSTS for builds. There is out of the box functionality for reporting code coverage totals in the build summary when using the cobertura format. However I'd also like to use the tool fdesjardins/coverage-viewer to generate a nice html report and it requires the standard json output.

I'm happy to do some work in this space but before I start I wanted to see what your opinion was on this.

I figure a nice way to access this functionality would be to allow comma separated values for CoverletOutputFormat. So in my case that would look like /p:CoverletOutputFormat=json,cobertura.

Looking at the code it should be pretty straight forward to implement.

[tonerdo]

@patros Thanks for pointing me to that tool, didn't even know it existed. This will be a good addition without breaking backwards compatibility

[coderpatros]

@tonerdo you're welcome. I have a pending pull request with fdesjardins to add support for Windows (and a couple of other minor issues), but short of that it's pretty good.

[hunterjm]

I’ve got a local build of coverlet that has ReportGenerator built in pending danielpalme/ReportGenerator#130. If that gets merged as is and the library package gets published, I’d be happy to open a PR.

Willing to open a separate issue as well to not hijack this one.

[tonerdo]

@patros all merged in!

[tonerdo]

New release here: https://www.nuget.org/packages/coverlet.msbuild/2.0.0