Add a setgitversion script to update the version string with git

.github/workflows/build.yml

@@ -16,9 +16,12 @@ jobs:
 
       - name: Checkout repository
         uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
 
       - name: Package Source
         run: |
+          ./setgitversion
           mkdir source
           cabal sdist
           mv dist-newstyle/sdist/*.tar.gz source/source.tar.gz