spruce up CI

.github/workflows/CI.yml

@@ -4,11 +4,9 @@ on:
   push:
     branches:
       - main
-      - master
   pull_request:
     branches:
       - main
-      - master
   schedule:
     # nightly tests, 2 am
     - cron: "0 2 * * *"
@@ -23,7 +21,7 @@ concurrency:
 
 defaults:
   run:
-    shell: bash -l {0}
+    shell: bash -leo pipefail {0}
 
 jobs:
   test:
@@ -36,18 +34,21 @@ jobs:
 
     steps:
     - uses: actions/[email protected]
+
+    - name: Get current date
+      id: date
+      run: echo "date=$(date +%Y-%m-%d)" >> "${GITHUB_OUTPUT}"
 
-    - uses: conda-incubator/setup-[email protected]
+    - uses: mamba-org/setup-micromamba@v1
       with:
-        python-version: "${{ matrix.python-version }}"
         environment-file: .binder/environment.yml
-        activate-environment: test
-        auto-activate-base: false
-        mamba-version: "*"
-        miniforge-version: latest
-        miniforge-variant: Mambaforge
-        use-mamba: true
-        channel-priority: true
+        cache-environment: true
+        cache-downloads: true
+        cache-environment-key: environment-${{ steps.date.outputs.date }}
+        cache-downloads-key: downloads-${{ steps.date.outputs.date }}
+        create-args: >-
+          python=${{ matrix.python-version }}
+        init-shell: bash
 
     - name: Additional info about the build
       run: |