Support rebase conflicts in check-merge-conflicts
diff --git a/pre_commit_hooks/check_merge_conflict.py b/pre_commit_hooks/check_merge_conflict.py
index d986998..7d87efc 100644
--- a/pre_commit_hooks/check_merge_conflict.py
+++ b/pre_commit_hooks/check_merge_conflict.py
@@ -15,7 +15,11 @@
 def is_in_merge():
     return (
         os.path.exists(os.path.join('.git', 'MERGE_MSG')) and
-        os.path.exists(os.path.join('.git', 'MERGE_HEAD'))
+        (
+            os.path.exists(os.path.join('.git', 'MERGE_HEAD')) or
+            os.path.exists(os.path.join('.git', 'rebase-apply')) or
+            os.path.exists(os.path.join('.git', 'rebase-merge'))
+        )
     )