Make the git gem optional

As it's not required or useful currently if Guix isn't available
locally.

2 files changed, 19 insertions, 13 deletions

diff --git a/app/jobs/govuk_guix/fetch_revision_job.rb b/app/jobs/govuk_guix/fetch_revision_job.rb
index d3f11bf..8d77761 100644
--- a/app/jobs/govuk_guix/fetch_revision_job.rb
+++ b/app/jobs/govuk_guix/fetch_revision_job.rb
@@ -18,8 +18,6 @@
 # License along with the GOV.UK Mini Environment Admin.  If not, see
 # <http://www.gnu.org/licenses/>.
 
-require 'git'
-
 class GovukGuix::FetchRevisionJob < Que::Job
   extend EnqueuedJobs
   include ::ShellUtils
@@ -82,8 +80,19 @@ class GovukGuix::FetchRevisionJob < Que::Job
         run_remotely_on_host: remote_host
       )
     else
+      require 'git'
+
       @repository_directory = 'tmp/cache/govuk-guix'
 
+      repository = if File.exist? @repository_directory
+                     Git.open(@repository_directory, log: Rails.logger)
+                   else
+                     Git.clone(
+                       self.class.repository_remote_location,
+                       @repository_directory
+                     )
+                   end
+
       repository.fetch
 
       sha = repository.object(commit_hash).sha
@@ -92,16 +101,6 @@ class GovukGuix::FetchRevisionJob < Que::Job
     end
   end
 
-  def repository
-    @_repository ||= begin
-      if File.exist? @repository_directory
-        Git.open(@repository_directory, log: Rails.logger)
-      else
-        Git.clone(self.class.repository_remote_location, @repository_directory)
-      end
-    end
-  end
-
   def available_services(store_path)
     command_output = run_command(
       "#{store_path}/bin/govuk",
diff --git a/config/boot.rb b/config/boot.rb
index d620a68..f39a63d 100644
--- a/config/boot.rb
+++ b/config/boot.rb
@@ -1,5 +1,11 @@
 require 'pathname'
 
+def activate_gem_if_available(name)
+  gem name
+rescue Gem::MissingSpecError
+  false
+end
+
 gem 'rails'
 gem 'sass-rails'
 
@@ -11,4 +17,5 @@ gem 'plek'
 gem 'que'
 gem 'ruby-terraform'
 gem 'with_advisory_lock'
-gem 'git'
+
+activate_gem_if_available 'git'