feat: 🎸 adds git hooks support

To run git-cz on `prepare-commit-msg` you can basically follow this
instruction
(https://github.com/commitizen/cz-cli#optional-running-commitizen-on-git-commit)
but usestreamich's `git-cz` instead of `cz-conventional-changelog`.

✅ Closes: #79

.eslintrc.json

@@ -3,6 +3,7 @@
   "rules": {
     "import/unambiguous": "off",
     "import/no-commonjs": "off",
+    "no-process-env": "off",
     "promise/prefer-await-to-then": "off",
     "strict": "off"
   }

lib/cli.js

@@ -1,10 +1,12 @@
 const {spawn} = require('child_process');
+const fs = require('fs');
 const shellescape = require('any-shell-escape');
 const minimist = require('minimist');
 const signale = require('signale');
 const createState = require('./createState');
 const runInteractiveQuestions = require('./runInteractiveQuestions');
 const formatCommitMessage = require('./formatCommitMessage');
+const getGitRootDir = require('./util/getGitRootDir');
 
 // eslint-disable-next-line no-process-env
 const executeCommand = (command, args = [], env = process.env) => {
@@ -31,7 +33,7 @@ const main = async () => {
       params[arg] = true;
     }
 
-    const {'dry-run': isDryRun, ...passThroughParams} = params;
+    const {'dry-run': isDryRun, hook: isHook, ...passThroughParams} = params;
 
     if (isDryRun) {
       // eslint-disable-next-line no-console
@@ -42,6 +44,18 @@ const main = async () => {
 
     const message = formatCommitMessage(state);
 
+    /**
+     * @author https://github.com/oxyii
+     * @see https://github.com/streamich/git-cz/issues/79
+     */
+    if (isHook) {
+      const commitMsgFile = getGitRootDir() + '/.git/COMMIT_EDITMSG';
+
+      fs.writeFileSync(commitMsgFile, message);
+      // eslint-disable-next-line no-process-exit
+      process.exit(0);
+    }
+
     const appendedArgs = [];
 
     // eslint-disable-next-line guard-for-in

package.json

@@ -49,7 +49,7 @@
   "husky": {
     "hooks": {
       "pre-commit": "yarn lint",
-      "prepare-commit-msg": "exec < /dev/tty && node ./bin/git-cz.js || true"
+      "prepare-commit-msg": "exec < /dev/tty && node ./bin/git-cz.js --hook || true"
     }
   },
   "config": {