style: add eslint to the project

The config is based on airbnb shared config, with some rules that work better with the project.

src/action.js

@@ -19,7 +19,7 @@ const configPath = resolve(
 
 const { context: eventContext } = github
 
-const pushEventHasOnlyOneCommit = from => {
+const pushEventHasOnlyOneCommit = (from) => {
   const gitEmptySha = '0000000000000000000000000000000000000000'
 
   return from === gitEmptySha
@@ -54,7 +54,7 @@ const getRangeForEvent = async () => {
     repo,
     pull_number: number,
   })
-  const commitShas = commits.map(commit => commit.sha)
+  const commitShas = commits.map((commit) => commit.sha)
   const [from] = commitShas
   const to = commitShas[commitShas.length - 1]
   // Git revision range doesn't include the "from" field in "git log", so for "from" we use the parent commit of PR's first commit
@@ -93,25 +93,25 @@ function getOptsFromConfig(config) {
   }
 }
 
-const formatErrors = lintedCommits =>
+const formatErrors = (lintedCommits) =>
   format(
-    { results: lintedCommits.map(commit => commit.lintResult) },
+    { results: lintedCommits.map((commit) => commit.lintResult) },
     {
       color: true,
       helpUrl: core.getInput('helpURL'),
     },
   )
 
-const hasOnlyWarnings = lintedCommits =>
+const hasOnlyWarnings = (lintedCommits) =>
   lintedCommits.length &&
   lintedCommits.every(({ lintResult }) => lintResult.valid) &&
   lintedCommits.some(({ lintResult }) => lintResult.warnings.length)
 
-const setFailed = formattedResults => {
+const setFailed = (formattedResults) => {
   core.setFailed(`You have commit messages with errors\n\n${formattedResults}`)
 }
 
-const handleOnlyWarnings = formattedResults => {
+const handleOnlyWarnings = (formattedResults) => {
   if (core.getInput('failOnWarnings') === 'true') {
     setFailed(formattedResults)
   } else {
@@ -126,7 +126,7 @@ const showLintResults = async ([from, to]) => {
     : await load({ extends: ['@commitlint/config-conventional'] })
   const opts = getOptsFromConfig(config)
   const lintedCommits = await Promise.all(
-    commits.map(async commit => ({
+    commits.map(async (commit) => ({
       lintResult: await lint(commit.message, config.rules, opts),
       hash: commit.hash,
     })),
@@ -144,7 +144,7 @@ const showLintResults = async ([from, to]) => {
   }
 }
 
-const exitWithMessage = message => error => {
+const exitWithMessage = (message) => (error) => {
   core.setFailed(`${message}\n${error.message}\n${error.stack}`)
 }
 

src/action.test.js

@@ -1,8 +1,9 @@
+/* eslint-disable global-require */
+/* eslint-env jest */
 const { git } = require('@commitlint/test')
 const execa = require('execa')
 const td = require('testdouble')
 const {
-  updateEnvVars,
   gitEmptyCommit,
   getCommitHashes,
   updatePushEnvVars,
@@ -147,7 +148,7 @@ describe('Commit Linter action', () => {
     await gitEmptyCommit(cwd, 'message from before push')
     await gitEmptyCommit(cwd, 'wrong message 1')
     await gitEmptyCommit(cwd, 'chore(WRONG): message 2')
-    const [before, , to] = await getCommitHashes(cwd)
+    const [, , to] = await getCommitHashes(cwd)
     await createPushEventPayload(cwd, { before: gitEmptySha, to })
     updatePushEnvVars(cwd, to)
     td.replace(process, 'cwd', () => cwd)
@@ -281,7 +282,7 @@ describe('Commit Linter action', () => {
           pull_number: '1',
         }),
       ).thenResolve({
-        data: [first, to].map(sha => ({ sha })),
+        data: [first, to].map((sha) => ({ sha })),
       })
       td.replace(process, 'cwd', () => cwd)
 

src/generateOutputs.js

@@ -2,7 +2,7 @@ const core = require('@actions/core')
 
 const resultsOutputId = 'results'
 
-const mapMessageValidation = item => item.message
+const mapMessageValidation = (item) => item.message
 
 const mapResultOutput = ({
   hash,
@@ -15,7 +15,7 @@ const mapResultOutput = ({
   warnings: warnings.map(mapMessageValidation),
 })
 
-const generateOutputs = lintedCommits => {
+const generateOutputs = (lintedCommits) => {
   const resultsOutput = lintedCommits.map(mapResultOutput)
 
   core.setOutput(resultsOutputId, resultsOutput)

src/gitCommits.js

@@ -7,12 +7,12 @@ const hashDelimiter = '--------->hash---------'
 
 const format = `%H${hashDelimiter}%B%n${commitDelimiter}`
 
-const buildGitArgs = gitOpts => {
+const buildGitArgs = (gitOpts) => {
   const { from, to, ...otherOpts } = gitOpts
-  var formatArg = `--format=${format}`
-  var fromToArg = [from, to].filter(Boolean).join('..')
+  const formatArg = `--format=${format}`
+  const fromToArg = [from, to].filter(Boolean).join('..')
 
-  var gitArgs = ['log', formatArg, fromToArg]
+  const gitArgs = ['log', formatArg, fromToArg]
 
   return gitArgs.concat(
     dargs(gitOpts, {
@@ -21,14 +21,14 @@ const buildGitArgs = gitOpts => {
   )
 }
 
-const gitCommits = async gitOpts => {
-  var args = buildGitArgs(gitOpts)
+const gitCommits = async (gitOpts) => {
+  const args = buildGitArgs(gitOpts)
 
-  var { stdout } = await execa('git', args, {
+  const { stdout } = await execa('git', args, {
     cwd: process.cwd(),
   })
 
-  const commits = stdout.split(`${commitDelimiter}\n`).map(messageItem => {
+  const commits = stdout.split(`${commitDelimiter}\n`).map((messageItem) => {
     const [hash, message] = messageItem.split(hashDelimiter)
 
     return {

src/testUtils.js

@@ -2,20 +2,21 @@ const path = require('path')
 const fs = require('fs')
 const { promisify } = require('util')
 const execa = require('execa')
-const td = require('testdouble')
 
 const writeFile = promisify(fs.writeFile)
 
-const updateEnvVars = (exports.updateEnvVars = envVars => {
-  Object.keys(envVars).forEach(key => {
+const updateEnvVars = (envVars) => {
+  Object.keys(envVars).forEach((key) => {
     process.env[key] = envVars[key]
   })
-})
+}
+
+exports.updateEnvVars = updateEnvVars
 
 exports.gitEmptyCommit = (cwd, message) =>
   execa('git', ['commit', '--allow-empty', '-m', message], { cwd })
 
-exports.getCommitHashes = async cwd => {
+exports.getCommitHashes = async (cwd) => {
   const { stdout } = await execa.command('git log --pretty=%H', { cwd })
   const hashes = stdout.split('\n').reverse()
 
@@ -45,7 +46,7 @@ exports.createPushEventPayload = async (
   await writeFile(eventPath, JSON.stringify(payload), 'utf8')
 }
 
-exports.createPullRequestEventPayload = async cwd => {
+exports.createPullRequestEventPayload = async (cwd) => {
   const payload = {
     number: '1',
     repository: {