Cache conda packages

Author: seisman

.github/workflows/ci_tests.yaml

@@ -30,12 +30,21 @@ jobs:
           # fecth all history so that versioneer works
           fetch-depth: 0
 
+      - name: Cache conda packages
+        uses: actions/cache@v2
+        with:
+          path: ${CONDA_PKGS_DIRS}
+          key: cache-conda-${{ github.ref }}-${{ hashFiles('environment.yml') }}
+          restore-keys: |
+            cache-conda-refs/heads/master-
+
       # Setup Miniconda
       - name: Setup Miniconda
         uses: goanpeca/[email protected]
         with:
           python-version: ${{ matrix.python-version }}
           channels: conda-forge
+          use-only-tar-bz2: true  # required for caching conda pacakges
 
       # Install GMT and other required dependencies from conda-forge
       - name: Install GMT and required dependencies