Use danger-gitlab to auto review merge requests

Given failures to check simple things in the past, like if a changelog
was present, danger-gitlab is introduced to automatically perform these
tasks.

A warning was added when a changelog entry is skipped, and failures are
due to missing MR descriptions or gitaly-proto versions being incorrect.

To force diff highlighting to work, `.gitattributes` was added.

3 files changed, 27 insertions, 0 deletions

diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 000000000..f1c41c9bb
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1 @@
+Dangerfile gitlab-language=ruby
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index deed4ed78..a2ed59b72 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -14,6 +14,13 @@ verify:
   script:
     - make verify
 
+danger-review:
+  stage: build
+  script:
+    - git version
+    - gem install danger-gitlab --no-document
+    - danger
+
 .ruby_template: &ruby_definition
   before_script:
     # Override gemfile config (for some reasong `config --delete` doesn't do it)
diff --git a/Dangerfile b/Dangerfile
new file mode 100644
index 000000000..c1ffd180f
--- /dev/null
+++ b/Dangerfile
@@ -0,0 +1,19 @@
+unless git.modified_files.include?("CHANGELOG.md")
+  warn("This MR is missing a CHANGLOG entry")
+end
+
+fail("Please provide a MR description") if gitlab.mr_body.empty?
+
+VENDOR_JSON = 'vendor/vendor.json'
+fail("Expected #{VENDOR_JSON} to exist") unless File.exist?(VENDOR_JSON)
+
+if git.modified_files.include?(VENDOR_JSON)
+  require 'json'
+  parsed_json = JSON.parse(File.read(VENDOR_JSON))
+
+  proto = parsed_json["package"]&.find { |h| h["path"].start_with?("gitlab.com/gitlab-org/gitaly-proto") }
+
+  unless proto["version"] && proto["version"] =~ /\Av\d+\./
+    fail("gitaly-proto version is incorrect")
+  end
+end