move formatter job to GitHub Actions

.github/workflows/formatter.yaml

@@ -0,0 +1,16 @@
+name: formatter
+on: [pull_request]
+jobs:
+  formatter:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout repo
+        uses: actions/checkout@v4
+      - name: install Julia
+        uses: julia-actions/setup-julia@v1
+        with:
+          version: 1.9
+      - name: Install Julia requirements
+        run: julia --project=${GITHUB_WORKSPACE}/.formatting -e 'import Pkg; Pkg.instantiate()'
+      - name: Check code style
+        run: julia --project=${GITHUB_WORKSPACE}/.formatting ${GITHUB_WORKSPACE}/.formatting/format_all.jl

.gitlab-ci.yml

@@ -1,23 +1,9 @@
 stages:
-  - linter
   - unit-test
   - generate_integration_test
   - run_integration_test
   - verify-unit-test-deps
 
-format:
-  stage: linter
-  image: julia:1.9
-  script:
-    - "[[ -d .julia ]] && mv .julia /tmp"
-    - julia --project=.formatting -e 'import Pkg; Pkg.instantiate()'
-    - julia --project=.formatting .formatting/format_all.jl
-    - "[[ -d /tmp/.julia ]] && mv /tmp/.julia ."
-  variables:
-    CI_JULIA_VERSION: "1.9"
-    JULIA_DEPOT_PATH: /tmp/.julia
-  allow_failure: true
-
 unit_tests_julia1.9:
   image: julia:1.9
   stage: unit-test