Make deps.pex cache repo scoped, so PRs and main commits share deps.p…

…ex (#197)

* Dont reuse the full deployment deps cache in PRs

This means the first PR action will rebuild the deps, however all subsequent PRs will be able to reuse the deps. 

If a PR changes deps then it will also get cached. Previous changing deps in a PR would rebuild the deps on each deploy.

actions/build_deploy_python_executable/action.yml

@@ -37,14 +37,11 @@ runs:
     - name: Set deps-cache-from
       # Don't use cached deps if instructed
       if: ${{ inputs.force_rebuild_deps != 'true' }}
-      # For PR commits, use the target branch name as the cache-tag, for other commits, use the branch name itself
-      run: echo "FLAG_DEPS_CACHE_FROM=--deps-cache-from=${{ github.repository }}/${{ github.base_ref && github.base_ref || github.ref_name }}" >> $GITHUB_ENV
+      run: echo "FLAG_DEPS_CACHE_FROM=--deps-cache-from=${{ github.repository }}" >> $GITHUB_ENV
       shell: bash
 
     - name: Set deps-cache-to
-      # Only write to the cache-tag for non PR commits so PR commits don't upgrade dependency versions
-      if: ${{ github.base_ref == '' }}
-      run: echo "FLAG_DEPS_CACHE_TO=--deps-cache-to=${{ github.repository }}/${{ github.ref_name }}" >> $GITHUB_ENV
+      run: echo "FLAG_DEPS_CACHE_TO=--deps-cache-to=${{ github.repository }}" >> $GITHUB_ENV
       shell: bash
 
     - name: Set up Python 3.8