Bring back call to symbolic-ref so that branch names are preferred ov…

…er tags. Closes dahlbyk#30

- git describe can pull a tag name instead of branch name
- symbolic-ref fails for tag names (so git describe is used instead)
- this code branch is only hit when EnableFileStatus is false or the branch name isn't found in 'git status'

GitUtils.ps1

@@ -44,6 +44,7 @@ function Get-GitBranch($gitDir = $(Get-GitDirectory), [Diagnostics.Stopwatch]$sw
 
             $b = '({0})' -f (
                 Coalesce-Args `
+                    { dbg 'Trying symbolic-ref' $sw; git symbolic-ref HEAD 2>$null } `
                     { dbg 'Trying describe' $sw; git describe --exact-match HEAD 2>$null } `
                     {
                         dbg 'Falling back on parsing HEAD' $sw