Add a default Lefthook configuration

- This adds a configuration file for Lefthook which is more flexible
  and powerful than Overcommit.
- The only downside is that if gather the diff between `origin/master`
  and `HEAD` so if you didn't fetch `origin/master` for a long time,
  the checks might be done on more files than the one that you updated.
- Also, that means you need a origin remote.
Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitignore

@@ -56,6 +56,7 @@ eslint-report.html
 /doc/code/*
 /dump.rdb
 /jsconfig.json
+/lefthook-local.yml
 /log/*.log*
 /node_modules
 /nohup.out

danger/commit_messages/Dangerfile

@@ -37,7 +37,8 @@ def build_message(commit, message, more_info: true)
 end
 
 def squash_mr?
-  gitlab_danger.ci? ? gitlab.mr_json['squash'] : false
+  # Locally, we assume the MR is set to be squashed so that the user only sees warnings instead of errors.
+  gitlab_danger.ci? ? gitlab.mr_json['squash'] : true
 end
 
 def wip_mr?
@@ -112,7 +113,7 @@ def lint_commits(commits)
 
     if multi_line_commit_linter && multi_line_commit_linter.failed?
       warn_or_fail_commits(multi_line_commit_linter)
-    else
+    elsif gitlab_danger.ci? # We don't have access to the MR title locally
       title_linter = lint_mr_title(gitlab.mr_json['title'])
       if title_linter.failed?
         warn_or_fail_commits(title_linter)

doc/development/contributing/style_guides.md

@@ -15,25 +15,35 @@ settings automatically by default. If your editor/IDE does not automatically sup
 we suggest investigating to see if a plugin exists. For instance here is the
 [plugin for vim](https://github.com/editorconfig/editorconfig-vim).
 
-## Pre-commit static analysis
+## Pre-push static analysis
 
-You should install [`overcommit`](https://github.com/sds/overcommit) to automatically check for
-static analysis offenses before committing locally.
+We strongly recommend installing
+[Lefthook](https://github.com/Arkweid/lefthook) to automatically check for
+static analysis offenses before pushing your changes.
 
 After installing `overcommit`, run the following in your GitLab source directory:
 
 ```shell
-make -C tooling/overcommit
+# Make sure to uninstall Overcommit first
+overcommit --uninstall
+
+# Install lefthook
+gem install lefthook && lefthook install -f
 ```
 
-Then before a commit is created, `overcommit` automatically checks for RuboCop (and other checks)
-offenses on every modified file.
+Before you push your changes, Lefthook will then automatically run Danger checks, as well
+as RuboCop, ES Lint, HAML Lint, and SCSS Lint for the changed files.
 
 This saves you time as you don't have to wait for the same errors to be detected by CI/CD.
 
-`overcommit` relies on a pre-commit hook to prevent commits that violate its ruleset. To override
-this behavior, pass the `OVERCOMMIT_DISABLE` environment variable. For example,
-`OVERCOMMIT_DISABLE=1 git rebase master` to rebase while disabling the Git hook.
+Lefthook relies on a pre-push hook to prevent commits that violate its ruleset.
+If you wish to override this behavior, pass the environment variable `LEFTHOOK=0`.
+That is, `LEFTHOOK=0 git push`.
+
+You can also:
+
+- Define [local configuration](https://github.com/Arkweid/lefthook/blob/master/docs/full_guide.md#local-config).
+- Skip [checks per tag on the fly](https://github.com/Arkweid/lefthook/blob/master/docs/full_guide.md#skip-some-tags-on-the-fly).
 
 ## Ruby, Rails, RSpec
 

doc/development/documentation/index.md

@@ -716,7 +716,7 @@ Sample configuration for `overcommit` is available in the
 file for the [`gitlab`](https://gitlab.com/gitlab-org/gitlab) project.
 
 To set up `overcommit` for documentation linting, see
-[Pre-commit static analysis](../contributing/style_guides.md#pre-commit-static-analysis).
+[Pre-commit static analysis](../contributing/style_guides.md#pre-push-static-analysis).
 
 #### Disable Vale tests
 

lefthook.yml

+pre-push:
+  parallel: true
+  commands:
+    danger:
+      run: bundle exec danger dry_run
+    eslint:
+      tags: frontend style
+      files: git diff --name-only $(git merge-base origin/master HEAD)..HEAD
+      glob: "*.{js,vue}"
+      run: yarn eslint --cache --max-warnings 0 --report-unused-disable-directives {files}
+    haml-lint:
+      tags: view haml style
+      files: git diff --name-only $(git merge-base origin/master HEAD)..HEAD
+      glob: "*.html.haml"
+      run: bundle exec haml-lint --config .haml-lint.yml {files}
+    scss-lint:
+      tags: stylesheet css style
+      files: git diff --name-only $(git merge-base origin/master HEAD)..HEAD
+      glob: "*.scss.css"
+      exclude: "app/assets/stylesheets/pages/emojis.scss"
+      run: bundle exec scss-lint --config .scss-lint.yml {files}
+    rubocop:
+      tags: backend style
+      files: git diff --name-only $(git merge-base origin/master HEAD)..HEAD
+      glob: "*.rb"
+      run: bundle exec rubocop --parallel --force-exclusion {files}

lib/gitlab/danger/helper.rb

@@ -168,7 +168,7 @@ module Gitlab
 
         %r{\A(\.gitlab-ci\.yml\z|\.gitlab\/ci)} => :engineering_productivity,
         %r{\A\.codeclimate\.yml\z} => :engineering_productivity,
-        %r{\A\.overcommit\.yml\.example\z} => :engineering_productivity,
+        %r{\Alefthook.yml\z} => :engineering_productivity,
         %r{\A\.editorconfig\z} => :engineering_productivity,
         %r{Dangerfile\z} => :engineering_productivity,
         %r{\A(ee/)?(danger/|lib/gitlab/danger/)} => :engineering_productivity,

spec/lib/gitlab/danger/helper_spec.rb

@@ -278,9 +278,9 @@ RSpec.describe Gitlab::Danger::Helper do
       'scripts/foo'                                           | [:engineering_productivity]
       'lib/gitlab/danger/foo'                                 | [:engineering_productivity]
       'ee/lib/gitlab/danger/foo'                              | [:engineering_productivity]
-      '.overcommit.yml.example'                               | [:engineering_productivity]
+      'lefthook.yml'                                          | [:engineering_productivity]
       '.editorconfig'                                         | [:engineering_productivity]
-      'tooling/overcommit/foo'                                | [:engineering_productivity]
+      'tooling/bin/find_foss_tests'                           | [:engineering_productivity]
       '.codeclimate.yml'                                      | [:engineering_productivity]
       '.gitlab/CODEOWNERS'                                    | [:engineering_productivity]