diff --git a/mercurial/changegroup.py b/mercurial/changegroup.py
--- a/mercurial/changegroup.py
+++ b/mercurial/changegroup.py
@@ -26,7 +26,6 @@
     phases,
     pycompat,
     repository,
-    revlog,
     util,
 )
 
@@ -716,7 +715,7 @@
                 p1node, p2node = adjustedparents[revision.node]
                 revision.p1node = p1node
                 revision.p2node = p2node
-                revision.flags |= revlog.REVIDX_ELLIPSIS
+                revision.flags |= repository.REVISION_FLAG_ELLIPSIS
 
         else:
             linknode = lookup(revision.node)
diff --git a/mercurial/help/internals/changegroups.txt b/mercurial/help/internals/changegroups.txt
--- a/mercurial/help/internals/changegroups.txt
+++ b/mercurial/help/internals/changegroups.txt
@@ -4,8 +4,8 @@
 
 There are 3 versions of changegroups: ``1``, ``2``, and ``3``. From a
 high-level, versions ``1`` and ``2`` are almost exactly the same, with the
-only difference being an additional item in the *delta header*.  Version
-``3`` adds support for revlog flags in the *delta header* and optionally
+only difference being an additional item in the *delta header*. Version
+``3`` adds support for storage flags in the *delta header* and optionally
 exchanging treemanifests (enabled by setting an option on the
 ``changegroup`` part in the bundle2).
 
@@ -127,6 +127,25 @@
 changegroup. This allows the delta to be expressed against any parent,
 which can result in smaller deltas and more efficient encoding of data.
 
+The *flags* field holds bitwise flags affecting the processing of revision
+data. The following flags are defined:
+
+32768
+   Censored revision. The revision's fulltext has been replaced by censor
+   metadata. May only occur on file revisions.
+16384
+   Ellipsis revision. Revision hash does not match data (likely due to rewritten
+   parents).
+8192
+   Externally stored. The revision fulltext contains ``key:value`` ``\n``
+   delimited metadata defining an object stored elsewhere. Used by the LFS
+   extension.
+
+For historical reasons, the integer values are identical to revlog version 1
+per-revision storage flags and correspond to bits being set in this 2-byte
+field. Bits were allocated starting from the most-significant bit, hence the
+reverse ordering and allocation of these flags.
+
 Changeset Segment
 =================
 
diff --git a/mercurial/repository.py b/mercurial/repository.py
--- a/mercurial/repository.py
+++ b/mercurial/repository.py
@@ -30,6 +30,13 @@
 # Repository supports being stream cloned.
 REPO_FEATURE_STREAM_CLONE = b'streamclone'
 
+REVISION_FLAG_CENSORED = 1 << 15
+REVISION_FLAG_ELLIPSIS = 1 << 14
+REVISION_FLAG_EXTSTORED = 1 << 13
+
+REVISION_FLAGS_KNOWN = (
+    REVISION_FLAG_CENSORED | REVISION_FLAG_ELLIPSIS | REVISION_FLAG_EXTSTORED)
+
 class ipeerconnection(interfaceutil.Interface):
     """Represents a "connection" to a repository.
 
@@ -375,7 +382,10 @@
         """20 byte node of the changelog revision this node is linked to.""")
 
     flags = interfaceutil.Attribute(
-        """2 bytes of integer flags that apply to this revision.""")
+        """2 bytes of integer flags that apply to this revision.
+
+        This is a bitwise composition of the ``REVISION_FLAG_*`` constants.
+        """)
 
     basenode = interfaceutil.Attribute(
         """20 byte node of the revision this data is a delta against.
@@ -658,7 +668,8 @@
         The data passed in already contains a metadata header, if any.
 
         ``node`` and ``flags`` can be used to define the expected node and
-        the flags to use with storage.
+        the flags to use with storage. ``flags`` is a bitwise value composed
+        of the various ``REVISION_FLAG_*`` constants.
 
         ``add()`` is usually called when adding files from e.g. the working
         directory. ``addrevision()`` is often called by ``add()`` and for
diff --git a/mercurial/revlogutils/constants.py b/mercurial/revlogutils/constants.py
--- a/mercurial/revlogutils/constants.py
+++ b/mercurial/revlogutils/constants.py
@@ -10,6 +10,7 @@
 from __future__ import absolute_import
 
 from .. import (
+    repository,
     util,
 )
 
@@ -28,9 +29,16 @@
 REVLOGV2_FLAGS = REVLOGV1_FLAGS
 
 # revlog index flags
-REVIDX_ISCENSORED = (1 << 15) # revision has censor metadata, must be verified
-REVIDX_ELLIPSIS = (1 << 14) # revision hash does not match data (narrowhg)
-REVIDX_EXTSTORED = (1 << 13) # revision data is stored externally
+
+# For historical reasons, revlog's internal flags were exposed via the
+# wire protocol and are even exposed in parts of the storage APIs.
+
+# revision has censor metadata, must be verified
+REVIDX_ISCENSORED = repository.REVISION_FLAG_CENSORED
+# revision hash does not match data (narrowhg)
+REVIDX_ELLIPSIS = repository.REVISION_FLAG_ELLIPSIS
+# revision data is stored externally
+REVIDX_EXTSTORED = repository.REVISION_FLAG_EXTSTORED
 REVIDX_DEFAULT_FLAGS = 0
 # stable order in which flags need to be processed and their processors applied
 REVIDX_FLAGS_ORDER = [
diff --git a/mercurial/testing/storage.py b/mercurial/testing/storage.py
--- a/mercurial/testing/storage.py
+++ b/mercurial/testing/storage.py
@@ -17,7 +17,7 @@
 from .. import (
     error,
     mdiff,
-    revlog,
+    repository,
 )
 from ..utils import (
     storageutil,
@@ -874,7 +874,7 @@
         with self._maketransactionfn() as tr:
             node0 = f.add(b'foo', None, tr, 0, nullid, nullid)
             f.addrevision(stored1, tr, 1, node0, nullid,
-                          flags=revlog.REVIDX_ISCENSORED)
+                          flags=repository.REVISION_FLAG_CENSORED)
 
         self.assertTrue(f.iscensored(1))
 
@@ -914,7 +914,7 @@
         f = self._makefilefn()
         with self._maketransactionfn() as tr:
             for i in range(15, 0, -1):
-                if (1 << i) & ~revlog.REVIDX_KNOWN_FLAGS:
+                if (1 << i) & ~repository.REVISION_FLAGS_KNOWN:
                     flags = 1 << i
                     break
 
diff --git a/tests/simplestorerepo.py b/tests/simplestorerepo.py
--- a/tests/simplestorerepo.py
+++ b/tests/simplestorerepo.py
@@ -371,7 +371,7 @@
     def iscensored(self, rev):
         validaterev(rev)
 
-        return self._flags(rev) & revlog.REVIDX_ISCENSORED
+        return self._flags(rev) & repository.REVISION_FLAG_CENSORED
 
     def commonancestorsheads(self, a, b):
         validatenode(a)
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -1038,8 +1038,8 @@
   
       There are 3 versions of changegroups: "1", "2", and "3". From a high-
       level, versions "1" and "2" are almost exactly the same, with the only
-      difference being an additional item in the *delta header*.  Version "3"
-      adds support for revlog flags in the *delta header* and optionally
+      difference being an additional item in the *delta header*. Version "3"
+      adds support for storage flags in the *delta header* and optionally
       exchanging treemanifests (enabled by setting an option on the
       "changegroup" part in the bundle2).
   
@@ -1162,6 +1162,27 @@
       changegroup. This allows the delta to be expressed against any parent,
       which can result in smaller deltas and more efficient encoding of data.
   
+      The *flags* field holds bitwise flags affecting the processing of revision
+      data. The following flags are defined:
+  
+      32768
+         Censored revision. The revision's fulltext has been replaced by censor
+         metadata. May only occur on file revisions.
+  
+      16384
+         Ellipsis revision. Revision hash does not match data (likely due to
+         rewritten parents).
+  
+      8192
+         Externally stored. The revision fulltext contains "key:value" "\n"
+         delimited metadata defining an object stored elsewhere. Used by the LFS
+         extension.
+  
+      For historical reasons, the integer values are identical to revlog version
+      1 per-revision storage flags and correspond to bits being set in this
+      2-byte field. Bits were allocated starting from the most-significant bit,
+      hence the reverse ordering and allocation of these flags.
+  
       Changeset Segment
       =================
   
@@ -3435,8 +3456,8 @@
   <p>
   There are 3 versions of changegroups: &quot;1&quot;, &quot;2&quot;, and &quot;3&quot;. From a
   high-level, versions &quot;1&quot; and &quot;2&quot; are almost exactly the same, with the
-  only difference being an additional item in the *delta header*.  Version
-  &quot;3&quot; adds support for revlog flags in the *delta header* and optionally
+  only difference being an additional item in the *delta header*. Version
+  &quot;3&quot; adds support for storage flags in the *delta header* and optionally
   exchanging treemanifests (enabled by setting an option on the
   &quot;changegroup&quot; part in the bundle2).
   </p>
@@ -3582,6 +3603,24 @@
   changegroup. This allows the delta to be expressed against any parent,
   which can result in smaller deltas and more efficient encoding of data.
   </p>
+  <p>
+  The *flags* field holds bitwise flags affecting the processing of revision
+  data. The following flags are defined:
+  </p>
+  <dl>
+   <dt>32768
+   <dd>Censored revision. The revision's fulltext has been replaced by censor metadata. May only occur on file revisions.
+   <dt>16384
+   <dd>Ellipsis revision. Revision hash does not match data (likely due to rewritten parents).
+   <dt>8192
+   <dd>Externally stored. The revision fulltext contains &quot;key:value&quot; &quot;\n&quot; delimited metadata defining an object stored elsewhere. Used by the LFS extension.
+  </dl>
+  <p>
+  For historical reasons, the integer values are identical to revlog version 1
+  per-revision storage flags and correspond to bits being set in this 2-byte
+  field. Bits were allocated starting from the most-significant bit, hence the
+  reverse ordering and allocation of these flags.
+  </p>
   <h2>Changeset Segment</h2>
   <p>
   The *changeset segment* consists of a single *delta group* holding