Fixed method to use git log via Popen as recommended, and made output match...

Fixed method to use git log via Popen as recommended, and made output match test (and thus system) expectations.

app/models/repository.rb

@@ -91,7 +91,12 @@ class Repository
     # Limited to 1000 commits for now, could be parameterized?
     args = %W(git log --pretty=%H --max-count 1000 --grep=#{query})
 
-    Gitlab::Popen.popen(args, path_to_repo)
+    git_log_results = Gitlab::Popen.popen(args, path_to_repo)
+
+    # 1. Get result, which is 1-element array
+    # 2. Split on lines
+    # 3. Recreate array, but remove trailing newline characters on each element
+    git_log_results.first.lines.map{ |l| l.chomp }
   end
 
   def find_branch(name)

spec/models/repository_spec.rb

@@ -27,7 +27,7 @@ describe Repository do
   end
 
   describe :find_commits_with_matching_log do
-    subject { repository.find_commits_with_matching_log('submodule').map{|k| k.id} }
+    subject { repository.find_commits_with_matching_log('submodule') }
 
     it { is_expected.to include('5937ac0a7beb003549fc5fd26fc247adbce4a52e') }
     it { is_expected.to include('6f6d7e7ed97bb5f0054f2b1df789b39ca89b6ff9') }