Support adding and removing labels w/ push opts

MergeRequests::PushOptionsHandlerService has been updated to allow
adding and removing labels to a merge request using git push options.

To create a new merge request and add 2 labels to it:

      git push -u origin -o merge_request.create \
        -o merge_request.label="My label 1" \
        -o merge_request.label="My label 2"

To update an existing merge request and remove a label while
adding a different label:

      git push -u origin -o merge_request.label="My added label" \
        -o merge_request.unlabel="My removed label"

Issue https://gitlab.com/gitlab-org/gitlab-ce/issues/64320

1 files changed, 19 insertions, 2 deletions

diff --git a/lib/gitlab/push_options.rb b/lib/gitlab/push_options.rb
index 682edfc4259..a2296d265cd 100644
--- a/lib/gitlab/push_options.rb
+++ b/lib/gitlab/push_options.rb
@@ -7,10 +7,12 @@ module Gitlab
         keys: [
           :create,
           :description,
+          :label,
           :merge_when_pipeline_succeeds,
           :remove_source_branch,
           :target,
-          :title
+          :title,
+          :unlabel
         ]
       },
       ci: {
@@ -18,6 +20,11 @@ module Gitlab
       }
     }).freeze
 
+    MULTI_VALUE_OPTIONS = [
+      %w[merge_request label],
+      %w[merge_request unlabel]
+    ].freeze
+
     NAMESPACE_ALIASES = HashWithIndifferentAccess.new({
       mr: :merge_request
     }).freeze
@@ -50,12 +57,22 @@ module Gitlab
         next if [namespace, key].any?(&:nil?)
 
         options[namespace] ||= HashWithIndifferentAccess.new
-        options[namespace][key] = value
+
+        if option_multi_value?(namespace, key)
+          options[namespace][key] ||= HashWithIndifferentAccess.new(0)
+          options[namespace][key][value] += 1
+        else
+          options[namespace][key] = value
+        end
       end
 
       options
     end
 
+    def option_multi_value?(namespace, key)
+      MULTI_VALUE_OPTIONS.any? { |arr| arr == [namespace, key] }
+    end
+
     def parse_option(option)
       parts = OPTION_MATCHER.match(option)
       return unless parts