[ci] add auto cargo-fmt (#1562)

* [WIP][ci] add auto cargo-fmt

* [ci] Apply cargo-fmt

* use fmt nightly

* [ci] Apply cargo-fmt

* add comment to cargo-fmt and remove fmt gha

Co-authored-by: paritytech-ci <paritytech-ci@parity.io>

.gitlab-ci.yml

@@ -69,6 +69,11 @@ variables:
  - if: $CI_COMMIT_REF_NAME =~ /^release-parachains-v[0-9].*$/ # i.e. release-parachains-v1.0, release-parachains-v2.1rc1, release-parachains-v3000
  - if: $CI_COMMIT_REF_NAME =~ /^polkadot-v[0-9]+\.[0-9]+.*$/ # i.e. polkadot-v1.0.99, polkadot-v2.1rc1
 
+.pr-refs: &pr-refs
+ # these jobs run always*
+ rules:
+ - if: $CI_COMMIT_REF_NAME =~ /^[0-9]+$/ # PRs
+
 .publish-refs: &publish-refs
  rules:
  - if: $CI_COMMIT_REF_NAME == "master"
@@ -107,6 +112,23 @@ variables:
  tags:
  - kubernetes-parity-build
 
+#### stage: .pre
+
+# checks code format and fails if formatting is required
+# the code will be formatted automatically and the pipeline will be restarted
+cargo-fmt:
+ stage: .pre
+ <<: *pr-refs
+ <<: *kubernetes-env
+ before_script:
+ - echo PROJECT_NAME=$CI_PROJECT_NAME > fmt.env
+ - echo PR_BRANCH_NAME=$(curl -s https://api.github.com/repos/paritytech/${CI_PROJECT_NAME}/pulls/${CI_COMMIT_REF_NAME} | jq -r ".head.ref") >> fmt.env
+ script:
+ - cargo +nightly fmt --check
+ artifacts:
+ reports:
+ dotenv: fmt.env
+
 #### stage: test
 
 test-linux-stable:
@@ -601,3 +623,17 @@ cancel-pipeline:
  project: "parity/infrastructure/ci_cd/pipeline-stopper"
  # remove branch, when pipeline-stopper for substrate and polakdot is updated to the same branch
  branch: "as-improve"
+
+# this job will automatically format code and rerun pipeline if cargo-fmt job fails
+auto-fmt:
+ stage: .post
+ rules:
+ - if: $CI_COMMIT_REF_NAME =~ /^[0-9]+$/ # PRs
+ when: on_failure
+ needs:
+ - job: cargo-fmt
+ variables:
+ PROJECT_NAME: "${CI_PROJECT_NAME}"
+ PR_BRANCH_NAME: "${PR_BRANCH_NAME}"
+ trigger:
+ project: "parity/infrastructure/ci_cd/auto-fmt"