From 34aa5570edf4ac89d3b54875cfb31299175dec98 Mon Sep 17 00:00:00 2001
From: George Kalpakas <kalpakas.g@gmail.com>
Date: Wed, 8 Apr 2020 23:56:05 +0300
Subject: [PATCH] fix(dev-infra): fix commit message validation in git
 worktrees (#36507)

Previously, the `pre-commit-validate` command (used in the `commit-msg`
git hook) assumed that the commit message was stored in
`.git/COMMIT_EDITMSG` file. This is usually true, but not when using
[git worktrees](https://git-scm.com/docs/git-worktree), where `.git` is
a file containing the path to the actual git directory.

This commit fixes it by taking advantage of the fact that git passes the
actual path of the file holding the commit message to the `commit-msg`
hook and husky exposes the arguments passed by git as
`$HUSKY_GIT_PARAMS`.

NOTE:
We cannot use the environment variable directly in the `commit-msg` hook
command, because environment variables need to be referenced differently
on Windows (`%VAR_NAME%`) vs macOS/Linux (`$VAR_NAME`). Instead, we pass
the name of the environment variable and the validation script reads the
variable's value off of `process.env`.

PR Close #36507
---
 dev-infra/commit-message/cli.ts           | 26 ++++++++++++++++++++---
 dev-infra/commit-message/validate-file.ts |  4 ++--
 package.json                              |  2 +-
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/dev-infra/commit-message/cli.ts b/dev-infra/commit-message/cli.ts
index aada6a3178..6e459d19d2 100644
--- a/dev-infra/commit-message/cli.ts
+++ b/dev-infra/commit-message/cli.ts
@@ -14,9 +14,29 @@ export function buildCommitMessageParser(localYargs: yargs.Argv) {
   return localYargs.help()
       .strict()
       .command(
-          'pre-commit-validate', 'Validate the most recent commit message', {},
-          () => {
-            validateFile('.git/COMMIT_EDITMSG');
+          'pre-commit-validate', 'Validate the most recent commit message', {
+            'file': {
+              type: 'string',
+              conflicts: ['file-env-variable'],
+              description: 'The path of the commit message file.',
+            },
+            'file-env-variable': {
+              type: 'string',
+              conflicts: ['file'],
+              description:
+                  'The key of the environment variable for the path of the commit message file.',
+              coerce: arg => {
+                const file = process.env[arg];
+                if (!file) {
+                  throw new Error(`Provided environment variable "${arg}" was not found.`);
+                }
+                return file;
+              },
+            }
+          },
+          args => {
+            const file = args.file || args.fileEnvVariable || '.git/COMMIT_EDITMSG';
+            validateFile(file);
           })
       .command(
           'validate-range', 'Validate a range of commit messages', {
diff --git a/dev-infra/commit-message/validate-file.ts b/dev-infra/commit-message/validate-file.ts
index b5c02555a9..9769caa33b 100644
--- a/dev-infra/commit-message/validate-file.ts
+++ b/dev-infra/commit-message/validate-file.ts
@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import {readFileSync} from 'fs';
-import {join} from 'path';
+import {resolve} from 'path';
 
 import {getRepoBaseDir} from '../utils/config';
 
@@ -14,7 +14,7 @@ import {validateCommitMessage} from './validate';
 
 /** Validate commit message at the provided file path. */
 export function validateFile(filePath: string) {
-  const commitMessage = readFileSync(join(getRepoBaseDir(), filePath), 'utf8');
+  const commitMessage = readFileSync(resolve(getRepoBaseDir(), filePath), 'utf8');
   if (validateCommitMessage(commitMessage)) {
     console.info('√  Valid commit message');
     return;
diff --git a/package.json b/package.json
index 0f2589f789..647c82bbb3 100644
--- a/package.json
+++ b/package.json
@@ -199,7 +199,7 @@
   "cldr-data-coverage": "full",
   "husky": {
     "hooks": {
-      "commit-msg": "yarn -s ng-dev commit-message pre-commit-validate"
+      "commit-msg": "yarn -s ng-dev commit-message pre-commit-validate --file-env-variable HUSKY_GIT_PARAMS"
     }
   }
 }