Support Review App Pipelines for MRs from Forks

2 files changed, 20 insertions, 4 deletions

diff --git a/lib/tasks/build_site.rake b/lib/tasks/build_site.rake
index 7b1fdadf..f9e1b807 100644
--- a/lib/tasks/build_site.rake
+++ b/lib/tasks/build_site.rake
@@ -9,7 +9,7 @@ task_helpers = TaskHelpers.new
 desc 'Clone Git repositories of documentation projects, keeping only the most recent commit'
 task :clone_repositories do
   task_helpers.products.each_value do |product|
-    branch = task_helpers.retrieve_branch(product['slug'])
+    branch, refspec = task_helpers.retrieve_branch(product['slug'])
 
     # Limit the pipeline to pull only the repo where the MR is, not all 4, to save time/space.
     # First we check if the branch on the docs repo is other than the default branch and
@@ -41,7 +41,14 @@ task :clone_repositories do
       end
     end
 
-    `git clone --branch #{branch} --single-branch #{product['repo']} --depth 1 #{product['project_dir']}`
+    Dir.mkdir(product['project_dir'])
+
+    Dir.chdir(product['project_dir']) do
+      `git -c init.defaultBranch=#{branch} init`
+      `git remote add origin #{product['repo']}`
+      `git fetch --depth 1 origin #{refspec}`
+      `git -c advice.detachedHead=false checkout FETCH_HEAD`
+    end
 
     latest_commit = `git -C #{product['project_dir']} log --oneline -n 1`
 
diff --git a/lib/tasks/task_helpers.rb b/lib/tasks/task_helpers.rb
index fd64afe6..d25ef043 100644
--- a/lib/tasks/task_helpers.rb
+++ b/lib/tasks/task_helpers.rb
@@ -32,12 +32,19 @@ class TaskHelpers
     # If we're NOT on a gitlab-docs stable branch, fetch the BRANCH_* environment
     # variable, and if not assigned, set to the default branch.
     #
-    return ENV.fetch("BRANCH_#{slug.upcase}", default_branch(products[slug].fetch('repo'))) if stable_branch_name.nil?
+    if stable_branch_name.nil?
+      merge_request_iid = ENV["MERGE_REQUEST_IID_#{slug.upcase}"]
+      branch_name = ENV.fetch("BRANCH_#{slug.upcase}", default_branch(products[slug].fetch('repo')))
+
+      return branch_name, "heads/#{branch_name}" if merge_request_iid.nil?
+
+      return branch_name, "merge-requests/#{merge_request_iid}/head"
+    end
 
     #
     # Check the project slug to determine the branch name
     #
-    case slug
+    stable_branch = case slug
 
     when 'ee'
       "#{stable_branch_name}-ee"
@@ -55,6 +62,8 @@ class TaskHelpers
     else
       default_branch(products[slug].fetch('repo'))
     end
+
+    return stable_branch, "heads/#{stable_branch}"
   end
 
   def git_workdir_dirty?