CI: tag release versions with commit count + hash

The format is `rnumberOfCommits.latestCommitHash`, i.e. `r23.a33dc14`. The repo has to be cloned with the whole commit history (not shallow) to get to number of commits, which is what `fetch-depth` does.

.github/workflows/c-cpp.yml

@@ -13,6 +13,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
+        with:
+          fetch-depth: '0'
+
       - name: Install dependency
         run: | 
           sudo apt-get update
@@ -21,12 +24,19 @@ jobs:
       - name: make
         run: | 
             make
+
+      - name: generate tag
+        id: tag
+        run: |
+          count=$(git rev-list --count HEAD)
+          hash=$(git rev-parse --short HEAD)
+          echo "::set-output name=tag::r${count}.${hash}"
         
       - uses: "marvinpinto/action-automatic-releases@latest"
         with:
             repo_token: "${{ secrets.GITHUB_TOKEN }}"
-            automatic_release_tag: "latest"
+            automatic_release_tag: "${{ steps.tag.outputs.tag }}"
             prerelease: false
-            title: "Release"
+            title: "Release ${{ steps.tag.outputs.tag }}"
             files: |
               *.efi