--- a/mercurial/exchangev2.py	Thu Feb 18 15:07:45 2021 +0100
+++ b/mercurial/exchangev2.py	Wed Mar 03 14:00:45 2021 +0100
@@ -22,6 +22,7 @@
     narrowspec,
     phases,
     pycompat,
+    requirements as requirementsmod,
     setdiscovery,
 )
 from .interfaces import repository
@@ -183,7 +184,7 @@
 
     # TODO This is super hacky. There needs to be a storage API for this. We
     # also need to check for compatibility with the remote.
-    if b'revlogv1' not in repo.requirements:
+    if requirementsmod.REVLOGV1_REQUIREMENT not in repo.requirements:
         return False
 
     return True

--- a/mercurial/localrepo.py	Thu Feb 18 15:07:45 2021 +0100
+++ b/mercurial/localrepo.py	Wed Mar 03 14:00:45 2021 +0100
@@ -974,7 +974,7 @@
     # opener options for it because those options wouldn't do anything
     # meaningful on such old repos.
     if (
-        b'revlogv1' in requirements
+        requirementsmod.REVLOGV1_REQUIREMENT in requirements
         or requirementsmod.REVLOGV2_REQUIREMENT in requirements
     ):
         options.update(resolverevlogstorevfsoptions(ui, requirements, features))
@@ -998,7 +998,7 @@
     options = {}
     options[b'flagprocessors'] = {}
 
-    if b'revlogv1' in requirements:
+    if requirementsmod.REVLOGV1_REQUIREMENT in requirements:
         options[b'revlogv1'] = True
     if requirementsmod.REVLOGV2_REQUIREMENT in requirements:
         options[b'revlogv2'] = True
@@ -1199,7 +1199,7 @@
     #    being successful (repository sizes went up due to worse delta
     #    chains), and the code was deleted in 4.6.
     supportedformats = {
-        b'revlogv1',
+        requirementsmod.REVLOGV1_REQUIREMENT,
         b'generaldelta',
         requirementsmod.TREEMANIFEST_REQUIREMENT,
         requirementsmod.COPIESSDC_REQUIREMENT,
@@ -3410,7 +3410,7 @@
             % createopts[b'backend']
         )
 
-    requirements = {b'revlogv1'}
+    requirements = {requirementsmod.REVLOGV1_REQUIREMENT}
     if ui.configbool(b'format', b'usestore'):
         requirements.add(b'store')
         if ui.configbool(b'format', b'usefncache'):
@@ -3458,7 +3458,7 @@
 
     revlogv2 = ui.config(b'experimental', b'revlogv2')
     if revlogv2 == b'enable-unstable-format-and-corrupt-my-data':
-        requirements.remove(b'revlogv1')
+        requirements.remove(requirementsmod.REVLOGV1_REQUIREMENT)
         # generaldelta is implied by revlogv2.
         requirements.discard(b'generaldelta')
         requirements.add(requirementsmod.REVLOGV2_REQUIREMENT)

--- a/mercurial/requirements.py	Thu Feb 18 15:07:45 2021 +0100
+++ b/mercurial/requirements.py	Wed Mar 03 14:00:45 2021 +0100
@@ -21,6 +21,8 @@
 # Stores manifest in Tree structure
 TREEMANIFEST_REQUIREMENT = b'treemanifest'
 
+REVLOGV1_REQUIREMENT = b'revlogv1'
+
 # Increment the sub-version when the revlog v2 format changes to lock out old
 # clients.
 REVLOGV2_REQUIREMENT = b'exp-revlogv2.1'

--- a/mercurial/streamclone.py	Thu Feb 18 15:07:45 2021 +0100
+++ b/mercurial/streamclone.py	Wed Mar 03 14:00:45 2021 +0100
@@ -20,6 +20,7 @@
     narrowspec,
     phases,
     pycompat,
+    requirements as requirementsmod,
     scmutil,
     store,
     util,
@@ -83,7 +84,7 @@
     # is advertised and contains a comma-delimited list of requirements.
     requirements = set()
     if remote.capable(b'stream'):
-        requirements.add(b'revlogv1')
+        requirements.add(requirementsmod.REVLOGV1_REQUIREMENT)
     else:
         streamreqs = remote.capable(b'streamreqs')
         # This is weird and shouldn't happen with modern servers.

--- a/mercurial/upgrade_utils/actions.py	Thu Feb 18 15:07:45 2021 +0100
+++ b/mercurial/upgrade_utils/actions.py	Wed Mar 03 14:00:45 2021 +0100
@@ -857,7 +857,7 @@
     """
     return {
         # Introduced in Mercurial 0.9.2.
-        b'revlogv1',
+        requirements.REVLOGV1_REQUIREMENT,
         # Introduced in Mercurial 0.9.2.
         b'store',
     }
@@ -937,7 +937,7 @@
         b'dotencode',
         b'fncache',
         b'generaldelta',
-        b'revlogv1',
+        requirements.REVLOGV1_REQUIREMENT,
         b'store',
         requirements.SPARSEREVLOG_REQUIREMENT,
         requirements.SIDEDATA_REQUIREMENT,

--- a/mercurial/wireprotov1server.py	Thu Feb 18 15:07:45 2021 +0100
+++ b/mercurial/wireprotov1server.py	Wed Mar 03 14:00:45 2021 +0100
@@ -27,6 +27,7 @@
     exchange,
     pushkey as pushkeymod,
     pycompat,
+    requirements as requirementsmod,
     streamclone,
     util,
     wireprototypes,
@@ -310,7 +311,7 @@
             caps.append(b'stream-preferred')
         requiredformats = repo.requirements & repo.supportedformats
         # if our local revlogs are just revlogv1, add 'stream' cap
-        if not requiredformats - {b'revlogv1'}:
+        if not requiredformats - {requirementsmod.REVLOGV1_REQUIREMENT}:
             caps.append(b'stream')
         # otherwise, add 'streamreqs' detailing our local revlog format
         else: