Use File.exist? to check if a repository exists

Initializing Rugged objects is way too expensive just to check if a
repository exists. Even though we cache this data once in a while we
have to refresh this. On GitLab.com we have seen Repository#exists?
taking up to _1 minute_ to complete in the absolute worst case, though
usually it sits around a second or so.

Using File.exist? to instead check if $GIT_DIR/refs exists is a much
faster way of checking if a repository was initialized properly.

1 files changed, 1 insertions, 2 deletions

diff --git a/spec/models/repository_spec.rb b/spec/models/repository_spec.rb
index 5e8a7bb08a1..635130cf797 100644
--- a/spec/models/repository_spec.rb
+++ b/spec/models/repository_spec.rb
@@ -811,8 +811,7 @@ describe Repository, models: true do
     end
 
     it 'returns false when a repository does not exist' do
-      expect(repository.raw_repository).to receive(:rugged).
-        and_raise(Gitlab::Git::Repository::NoRepository)
+      allow(repository).to receive(:refs_directory_exists?).and_return(false)
 
       expect(repository.exists?).to eq(false)
     end