feat(semantic-release): configure for this formula

* https://github.com/semantic-release/semantic-release
  - Fully automated version management and package publishing.
* This commit introduces automation for the following processes:
  - (1) Version number bumped based on commit message types.
  - (2) Tags and releases created in GitHub.
  - (3) Changelog updated using the same content in the GitHub release.
  - (4) `FORMULA` version number updated.
  - (5) PR comments sent to inform which release includes the changes.

.travis.yml

@@ -17,3 +17,26 @@ env:
 script:
   - bundle exec kitchen verify ${INSTANCE}
 
+before_deploy:
+  # Only deploy if the build passed successfully
+  - test $TRAVIS_TEST_RESULT = 0
+
+jobs:
+  # Only run if this is the `master` branch
+  if: branch = master
+  include:
+    # Define the release stage that runs semantic-release
+    - stage: release
+      language: node_js
+      node_js: lts/*
+      before_install: skip
+      script:
+        - npm install @semantic-release/changelog@3 -D
+        - npm install @semantic-release/exec@3 -D
+        - npm install @semantic-release/git@7 -D
+      deploy:
+        provider: script
+        skip_cleanup: true
+        script:
+          - npx semantic-release@15
+

README.rst

@@ -2,6 +2,13 @@
 template-formula
 ================
 
+|img_travis| |img_sr|
+
+.. |img_travis| image:: https://travis-ci.com/saltstack-formulas/template-formula.svg?branch=master
+    :target: https://travis-ci.com/saltstack-formulas/template-formula
+.. |img_sr| image:: https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg
+    :target: https://github.com/semantic-release/semantic-release
+
 A SaltStack formula that is empty. It has dummy content to help with a quick
 start on a new formula and it serves as a style guide.
 

release-rules.js

@@ -0,0 +1,16 @@
+// No release is triggered for the types commented out below.
+// Commits using these types will be incorporated into the next release.
+module.exports = [
+  {breaking: true, release: 'major'},
+  // {type: 'build', release: 'patch'},
+  // {type: 'chore', release: 'patch'},
+  // {type: 'ci', release: 'patch'},
+  {type: 'docs', release: 'patch'},
+  {type: 'feat', release: 'minor'},
+  {type: 'fix', release: 'patch'},
+  {type: 'perf', release: 'patch'},
+  {type: 'refactor', release: 'patch'},
+  {type: 'revert', release: 'patch'},
+  {type: 'style', release: 'patch'},
+  {type: 'test', release: 'patch'},
+];

release.config.js

@@ -0,0 +1,103 @@
+module.exports = {
+  branch: 'master',
+  plugins: [
+      ['@semantic-release/commit-analyzer', {
+        preset: 'angular',
+        releaseRules: './release-rules.js',
+      }],
+      '@semantic-release/release-notes-generator',
+      ['@semantic-release/changelog', {
+        changelogFile: 'CHANGELOG.md',
+        changelogTitle: '# Changelog',
+      }],
+      ['@semantic-release/exec', {
+        prepareCmd: 'sh ./update_FORMULA.sh ${nextRelease.version}',
+      }],
+      ['@semantic-release/git', {
+        assets: ['CHANGELOG.md', 'FORMULA'],
+      }],
+      '@semantic-release/github',
+  ],
+  generateNotes: {
+    preset: 'angular',
+    writerOpts: {
+      // Required due to upstream bug preventing all types being displayed.
+      // Bug: https://github.com/conventional-changelog/conventional-changelog/issues/317
+      // Fix: https://github.com/conventional-changelog/conventional-changelog/pull/410
+      transform: (commit, context) => {
+          const issues = []
+
+          commit.notes.forEach(note => {
+              note.title = `BREAKING CHANGES`
+          })
+
+          if (commit.type === `feat`) {
+              commit.type = `Features`
+          } else if (commit.type === `fix`) {
+              commit.type = `Bug Fixes`
+          } else if (commit.type === `perf`) {
+              commit.type = `Performance Improvements`
+          } else if (commit.type === `revert`) {
+              commit.type = `Reverts`
+          } else if (commit.type === `docs`) {
+              commit.type = `Documentation`
+          } else if (commit.type === `style`) {
+              commit.type = `Styles`
+          } else if (commit.type === `refactor`) {
+              commit.type = `Code Refactoring`
+          } else if (commit.type === `test`) {
+              commit.type = `Tests`
+          } else if (commit.type === `build`) {
+              commit.type = `Build System`
+          } else if (commit.type === `ci`) {
+              commit.type = `Continuous Integration`
+          } else {
+              return
+          }
+
+          if (commit.scope === `*`) {
+              commit.scope = ``
+          }
+
+          if (typeof commit.hash === `string`) {
+              commit.hash = commit.hash.substring(0, 7)
+          }
+
+          if (typeof commit.subject === `string`) {
+              let url = context.repository
+                  ? `${context.host}/${context.owner}/${context.repository}`
+                  : context.repoUrl
+              if (url) {
+                  url = `${url}/issues/`
+                  // Issue URLs.
+                  commit.subject = commit.subject.replace(/#([0-9]+)/g, (_, issue) => {
+                      issues.push(issue)
+                      return `[#${issue}](${url}${issue})`
+                  })
+              }
+              if (context.host) {
+                  // User URLs.
+                  commit.subject = commit.subject.replace(/\B@([a-z0-9](?:-?[a-z0-9/]){0,38})/g, (_, username) => {
+                  if (username.includes('/')) {
+                      return `@${username}`
+                  }
+
+                  return `[@${username}](${context.host}/${username})`
+                  })
+              }
+          }
+
+          // remove references that already appear in the subject
+          commit.references = commit.references.filter(reference => {
+              if (issues.indexOf(reference.issue) === -1) {
+                  return true
+              }
+
+              return false
+          })
+
+          return commit
+      },
+    },
+  },
+};

update_FORMULA.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+sed -i -e "s_^\(version:\).*_\1 ${1}_" FORMULA