--- a/mercurial/repository.py	Wed Sep 26 14:41:15 2018 -0700
+++ b/mercurial/repository.py	Fri Oct 19 14:59:03 2018 +0200
@@ -29,6 +29,8 @@
 REPO_FEATURE_LFS = b'lfs'
 # Repository supports being stream cloned.
 REPO_FEATURE_STREAM_CLONE = b'streamclone'
+# Files storage may lack data for all ancestors.
+REPO_FEATURE_SHALLOW_FILE_STORAGE = b'shallowfilestorage'
 
 REVISION_FLAG_CENSORED = 1 << 15
 REVISION_FLAG_ELLIPSIS = 1 << 14