v3: allow filtering branches by exists_on_github

lib/travis/api/v3/queries/branches.rb

@@ -1,5 +1,7 @@
 module Travis::API::V3
   class Queries::Branches < Query
+    params :exists_on_github, prefix: :branch
+
     sortable_by :name,
       last_build: "builds.started_at".freeze,
       exists_on_github: "(case when branches.exists_on_github then 1 else 2 end)".freeze
@@ -7,7 +9,12 @@ module Travis::API::V3
     default_sort "last_build:desc"
 
     def find(repository)
-      sort repository.branches
+      sort filter(repository.branches)
+    end
+
+    def filter(list)
+      list = list.where(exists_on_github: bool(exists_on_github)) unless exists_on_github.nil?
+      list
     end
   end
 end

lib/travis/api/v3/services/branches/find.rb

@@ -1,5 +1,6 @@
 module Travis::API::V3
   class Services::Branches::Find < Service
+    params :exists_on_github, prefix: :branch
     paginate
 
     def run!

spec/v3/services/branches/find_spec.rb

@@ -172,6 +172,20 @@ describe Travis::API::V3::Services::Branches::Find do
     }
   end
 
+  describe "filtering by exists_on_github" do
+    describe "false" do
+      before     { get("/v3/repo/#{repo.id}/branches?branch.exists_on_github=false") }
+      example    { expect(last_response).to be_ok }
+      example    { expect(parsed_body["branches"]).to be_empty }
+    end
+
+    describe "true" do
+      before     { get("/v3/repo/#{repo.id}/branches?branch.exists_on_github=true") }
+      example    { expect(last_response).to be_ok }
+      example    { expect(parsed_body["branches"]).not_to be_empty }
+    end
+  end
+
   describe "sorting by name" do
     before  { get("/v3/repo/#{repo.id}/branches?sort_by=name&limit=1") }
     example { expect(last_response).to be_ok }