remove contains check in Repository::checkout (problematic in conjunction with...

remove contains check in Repository::checkout (problematic in conjunction with the copy method and the git call will fail anyway if the commit id is invalid), copy commits in Repository::copy

src/de/uni_passau/fim/seibt/gitwrapper/repo/Repository.java

@@ -66,12 +66,6 @@ public class Repository {
      * @see <a href=https://git-scm.com/docs/git-checkout>git checkout</a>
      */
     public boolean checkout(Commit c) {
-
-        if (!commits.containsValue(c)) {
-            LOG.warning(() -> String.format("Checkout failed. %s is not part of %s.", c, this));
-            return false;
-        }
-
         Optional<ExecRes> checkout = git.exec(dir, "checkout", c.getId());
         Function<ExecRes, Boolean> toBoolean = res -> {
             boolean failed = git.failed(res);
@@ -240,7 +234,13 @@ public class Repository {
             return Optional.empty();
         }
 
-        return Optional.of(new Repository(git, url, destination));
+        Repository repo = new Repository(git, url, destination);
+
+        for (Map.Entry<String, Commit> entry : commits.entrySet()) {
+            repo.getCommitUnchecked(entry.getValue().getId());
+        }
+
+        return Optional.of(repo);
     }
 
     /**