Add "PR doctor" script

Gemfile

@@ -4,6 +4,7 @@ gem "httparty"
 gem "octokit"
 
 group :development, :test do
+  gem "byebug"
   gem "rspec"
   gem "rubocop-govuk", require: false
   gem "timecop"

Gemfile.lock

@@ -16,6 +16,7 @@ GEM
     ast (2.4.2)
     base64 (0.1.1)
     bigdecimal (3.1.4)
+    byebug (11.1.3)
     concurrent-ruby (1.2.2)
     connection_pool (2.4.1)
     crack (0.4.5)
@@ -111,6 +112,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  byebug
   httparty
   octokit
   rspec

README.md

@@ -43,6 +43,22 @@ To run the tests:
 bundle exec rspec
 ```
 
+### Using the merger locally
+
+The repo expects an `AUTO_MERGE_TOKEN` environment variable to be defined. This should be a GitHub API token [with sufficient scope](./docs/adr/03-access-token-scope.md).
+
+You can then run the merger with:
+
+```
+bundle exec ruby bin/merge_dependabot_prs.rb
+```
+
+The repo also ships with a "doctor" script to help you to debug individual PRs and why they did or did not auto-merge.
+
+```
+bundle exec ruby bin/pr_doctor.rb https://github.com/alphagov/content-data-api/pull/1996
+```
+
 ### Further documentation
 
 - [ADR 1: Limited team access to avoid privilege escalation](./docs/adr/01-limited-team-access.md)

bin/pr_doctor.rb

@@ -0,0 +1,7 @@
+require_relative "../lib/auto_merger"
+
+raise "Expecting exactly one argument, e.g. `ruby bin/pr_doctor.rb https://github.com/alphagov/content-data-api/pull/1996`" unless ARGV.count == 1
+
+pr_url = ARGV.first
+
+AutoMerger.analyse_dependabot_pr(pr_url)

lib/auto_merger.rb

@@ -1,4 +1,5 @@
 require_relative "./bank_holiday_checker"
+require_relative "./repo"
 require_relative "./repos"
 
 class AutoMerger
@@ -29,4 +30,13 @@ def merge_dependabot_prs
       end
     end
   end
+
+  def self.analyse_dependabot_pr(url)
+    puts "Analysing #{url}..."
+    _, repo_name, pr_number = url.match(/alphagov\/(.+)\/pull\/(.+)$/).to_a
+    pr = Repo.new(repo_name).dependabot_pull_request(pr_number)
+
+    puts pr.is_auto_mergeable? ? "PR is considered auto-mergeable." : "PR is not considered auto-mergeable."
+    puts 'Add `require "byebug"; byebug` inside the `is_auto_mergeable?` method to find out more.'
+  end
 end

lib/repo.rb

@@ -17,4 +17,8 @@ def dependabot_pull_requests
       .select { |api_response| api_response.user.login == "dependabot[bot]" }
       .map { |api_response| PullRequest.new(api_response) }
   end
+
+  def dependabot_pull_request(pr_number)
+    PullRequest.new(GitHubClient.instance.pull_request("alphagov/#{@repo_name}", pr_number))
+  end
 end