Preserve existing file encoding if it can be easily determined otherwise use UTF8 with BOM.

[kll]

This fixes #1074 and will no longer strip the BOM or change the encoding when a file has a BOM. It does not handle cases where a BOM was not included or the existing encoding was not Unicode based. In those cases the files will be written using UTF8 with BOM as that is the most common and complies with StyleCop SA1412

[kll]

At the moment it looks like the travis-ci MacOS queue is having some issues.

[kll]

Yesterday when I submitted the PR the appveyor build passed but the travis-ci build failed due to their MacOS queue issues. Today I nudged the PR to cause a rebuild since travis-ci was back to normal but this time the inverse happened and appveyor failed while travis-ci passed. No code changed and looking at the log everything built and it shows 431 tests passed, 0 failed, 0 warnings, 0 inconclusive, 0 skipped. It just looks like NUnit3 crashed.

[asbjornu]

Seems like the problem is this:

Error : C:\projects\gitversion\src\GitVersionTask.Tests\bin\Release\GitVersionTask.Tests.dll
Object reference not set to an instance of an object.
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at NUnit.Engine.Services.TestAgency.LaunchAgentProcess(TestPackage package)
   at NUnit.Engine.Services.TestAgency.CreateRemoteAgent(TestPackage package, Int32 waitTime)
   at NUnit.Engine.Runners.ProcessRunner.CreateAgentAndRunner()
   at NUnit.Engine.Runners.ProcessRunner.RunTests(ITestEventListener listener, TestFilter filter)

Perhaps upgrading NUnit can help?

[kll]

I don't know, maybe it will, but why did it run and pass the day before? It also runs and passes fine when I run the build locally. I suspect something transient on the appveyor server and if it was just run again it would probably pass.

[asbjornu]

@kll: Ok, I've restarted the build. Let's see how it goes.