gitversion: support forks/RCs/dirty Git versions

Enhance the GitVersion type to be aware of different forks of Git
including Git for Windows, Microsoft, and Apple.

Also add support for release candidates found in the version string -
these can appear as either a -rcN or .rcN format depending on if this is
a tag or a build version. We support both types.

Finally also capture the Commit ID from a dirty build version, i.e,
<major>.<minor>.<patch>.g<sha>

Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com>

Author: mjcheetham

src/shared/Core.Tests/GitTests.cs

@@ -197,8 +197,7 @@ public void Git_Version_ReturnsVersion()
             var git = new GitProcess(trace, trace2, processManager, gitPath, Path.GetTempPath());
             GitVersion version = git.Version;
 
-            Assert.NotEqual(new GitVersion(), version);
-
+            Assert.NotEqual(GitVersion.Zero, version);
         }
 
         #region Test Helpers