Bump minimum supported Swift version to 5.5

## Motivation

RediStack 1.x is going to be supported at least until 2.x is released, which is a few months away.

Developers who are on later versions of Swift will adopt later versions of NIO and other libraries, and after we merged !183 we required NIO 2.42.x which has a minimum Swift version of 5.5

## Changes

This back ports the CI config from `master` into this branch, with updates to the README to reflect the changes

Author: Mordil

.gitlab/ci/amazonlinux-2.yml

@@ -1,22 +1,25 @@
-include: '/.gitlab/ci/test-template.yml'
+include: '/.gitlab/ci/platform-test.yml'
 
-.centos7-test-workaround:
-  extends: .unit-test
+.centos7:
+  extends: .platform-test
   before_script:
     - yum install -y make libcurl-devel
     - git clone https://github.com/git/git -bv2.28.0 --depth 1
     - cd git
     - make prefix=/usr -j all install NO_OPENSSL=1 NO_EXPAT=1 NO_TCLTK=1 NO_GETTEXT=1 NO_PERL=1
 
 swift trunk:
-  extends: .centos7-test-workaround
-  image: swiftlang/swift:nightly-master-centos7
-  allow_failure: true
+  extends: .centos7
+  image: swiftlang/swift:nightly-main-centos7
 
-swift 5.3:
-  extends: .centos7-test-workaround
-  image: swift:5.3-centos7
+swift 5.7:
+  extends: .centos7
+  image: swiftlang/swift:nightly-5.7-centos7
 
-swift 5.2:
-  extends: .centos7-test-workaround
-  image: swift:5.2-centos7
+swift 5.6:
+  extends: .centos7
+  image: swift:5.6-centos7
+
+swift 5.5:
+  extends: .centos7
+  image: swift:5.5-centos7

.gitlab/ci/centos-7.yml

@@ -0,0 +1,5 @@
+include: '/.gitlab/ci/platform-test.yml'
+
+swift 5.5:
+  extends: .platform-test
+  image: swift:5.5-${SWIFT_PLATFORM_NAME}

.gitlab/ci/centos-8.yml

@@ -1,37 +1,8 @@
+include: '/.gitlab/ci/platform-test.yml'
+
 stages:
   - Platform Tests
   - Quality Checks
-  - Docs
- 
-pages:
-  stage: Docs
-  only:
-    - tags
-  image: norionomura/jazzy
-  tags:
-    - docker
-  variables:
-    MODULE_NAME: "RediStack"
-    REPO_URL: "https://gitlab.com/mordil/swift-redi-stack"
-  script: |
-    export VERSION=$(git describe --abbrev=0 --tags || echo "0.0.0")
-    swift build
-    sourcekitten doc --spm-module "$MODULE_NAME" > "./$MODULE_NAME.json"
-    jazzy --clean \
-          --author "Nathan Harris (Mordil)" \
-          --readme "./README.md" \
-          --author_url "https://www.mordil.info" \
-          --github_url "$REPO_URL" \
-          --github-file-prefix "$REPO_URL/blob/$VERSION" \
-          --root-url "https://mordil.gitlab.io/swift-redi-stack/" \
-          --module "$MODULE_NAME" \
-          --module-version "$VERSION" \
-          --theme docs/theme \
-          --sourcekitten-sourcefile "./$MODULE_NAME.json" \
-          --output "./public"
-  artifacts:
-    paths:
-      - public
 
 Code Climate:
   only:
@@ -58,38 +29,56 @@ Code Climate:
     reports:
       codequality: gl-code-quality-report.json
 
-Ubuntu Bionic:
+Code Coverage:
+  extends: .platform-test
+  stage: Quality Checks
+  allow_failure: false
+  image: swift:latest
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+      changes:
+        - '*.swift'
+  script: scripts/generate_code_coverage.sh
+  coverage: '/TOTAL.*(\s\d+\.\d+%)/'
+
+.standard-platform-test:
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "push"
   stage: Platform Tests
   trigger:
     strategy: depend
-    include: '/.gitlab/ci/ubuntu-bionic.yml'
+    include: '/.gitlab/ci/standard-platforms.yml'
 
 Ubuntu Xenial:
-  stage: Platform Tests
+  extends: .standard-platform-test
+  variables:
+    SWIFT_PLATFORM_NAME: xenial
   trigger:
-    strategy: depend
-    include: '/.gitlab/ci/ubuntu-xenial.yml'
+    include: '/.gitlab/ci/eol-platforms-5.5.yml'
+
+Ubuntu Bionic:
+  extends: .standard-platform-test
+  variables:
+    SWIFT_PLATFORM_NAME: bionic
 
 Ubuntu Focal:
-  stage: Platform Tests
-  trigger:
-    strategy: depend
-    include: '/.gitlab/ci/ubuntu-focal.yml'
+  extends: .standard-platform-test
+  variables:
+    SWIFT_PLATFORM_NAME: focal
 
 CentOS 7:
-  stage: Platform Tests
+  extends: .standard-platform-test
   trigger:
-    strategy: depend
     include: '/.gitlab/ci/centos-7.yml'
 
 CentOS 8:
-  stage: Platform Tests
+  extends: .standard-platform-test
+  variables:
+    SWIFT_PLATFORM_NAME: centos8
   trigger:
-    strategy: depend
-    include: '/.gitlab/ci/centos-8.yml'
+    include: '/.gitlab/ci/eol-platforms-5.5.yml'
 
 Amazon Linux 2:
-  stage: Platform Tests
-  trigger:
-    strategy: depend
-    include: '/.gitlab/ci/amazonlinux-2.yml'
+  extends: .standard-platform-test
+  variables:
+    SWIFT_PLATFORM_NAME: amazonlinux2

.gitlab/ci/eol-platforms-5.5.yml

@@ -1,8 +1,9 @@
 stages:
   - Test
 
-.unit-test:
+.platform-test:
   stage: Test
+  allow_failure: true
   tags:
     - docker
   variables:

.gitlab/ci/main.yml

@@ -0,0 +1,17 @@
+include: '/.gitlab/ci/platform-test.yml'
+
+swift trunk:
+  extends: .platform-test
+  image: swiftlang/swift:nightly-main-${SWIFT_PLATFORM_NAME}  
+
+swift 5.7:
+  extends: .platform-test
+  image: swiftlang/swift:nightly-5.7-${SWIFT_PLATFORM_NAME}
+
+swift 5.6:
+  extends: .platform-test
+  image: swift:5.6-${SWIFT_PLATFORM_NAME}
+
+swift 5.5:
+  extends: .platform-test
+  image: swift:5.5-${SWIFT_PLATFORM_NAME}