Handle case where git rev-list returns an error

Author: jawshooah

lib/overcommit/exceptions.rb

@@ -11,6 +11,9 @@ class GitConfigError < StandardError; end
   # Raised when there was a problem reading submodule information for a repo.
   class GitSubmoduleError < StandardError; end
 
+  # Raised when there was a problem reading git revision information with `rev-list`.
+  class GitRevListError < StandardError; end
+
   # Raised when a {HookContext} is unable to setup the environment before a run.
   class HookSetupFailed < StandardError; end
 

lib/overcommit/hook_context/pre_push.rb

@@ -41,7 +41,14 @@ def to_s
       private
 
       def overwritten_commits
-        `git rev-list #{remote_sha1} ^#{local_sha1}`.split("\n")
+        return @overwritten_commits if defined? @overwritten_commits
+        result = Overcommit::Subprocess.spawn(%W[git rev-list #{remote_sha1} ^#{local_sha1}])
+        if result.success?
+          result.stdout.split("\n")
+        else
+          raise Overcommit::Exceptions::GitRevListError,
+                "Unable to check if commits on the remote ref will be overwritten: #{result.stderr}"
+        end
       end
     end
   end

spec/overcommit/hook_context/pre_push_spec.rb

@@ -89,6 +89,21 @@
 
         it { should == true }
       end
+
+      context 'when remote ref head does not exist locally' do
+        let(:git_error_msg) { "fatal: bad object #{remote_sha1}" }
+
+        before do
+          pushed_ref.stub(created?: false, deleted?: false)
+          result = double(success?: false, stderr: git_error_msg)
+          Overcommit::Subprocess.stub(:spawn).and_return(result)
+        end
+
+        it 'should raise' do
+          expect { subject }.to raise_error(Overcommit::Exceptions::GitRevListError,
+                                            /#{git_error_msg}/)
+        end
+      end
     end
 
     describe '#created?' do