Add helper for checking whether a repo has commits

I'm doing it this way instead of calling GetRepoFromPath directly from
the calling site because I don't want GitHub.VisualStudio to have an
explicit reference to libgit2sharp, and I'm not sure if I want to add
this to the ISimpleRepositoryModel interface.

Author: shana

src/GitHub.Exports/Services/Services.cs

@@ -180,5 +180,11 @@ public static UriString GetUriFromRepository(this IGitRepositoryInfo repoInfo)
         {
             return repoInfo.GetRepoFromIGit()?.GetUri();
         }
+
+        public static bool HasCommits(this ISimpleRepositoryModel repository)
+        {
+            var repo = GetRepoFromPath(repository.LocalPath);
+            return repo?.Commits.Count() > 0;
+        }
     }
 }