--- a/mercurial/localrepo.py	Sat Aug 08 16:24:12 2020 +0530
+++ b/mercurial/localrepo.py	Sat Aug 08 16:37:59 2020 +0530
@@ -426,30 +426,6 @@
     # End of baselegacywirecommands interface.
 
 
-# Increment the sub-version when the revlog v2 format changes to lock out old
-# clients.
-REVLOGV2_REQUIREMENT = b'exp-revlogv2.1'
-
-# A repository with the sparserevlog feature will have delta chains that
-# can spread over a larger span. Sparse reading cuts these large spans into
-# pieces, so that each piece isn't too big.
-# Without the sparserevlog capability, reading from the repository could use
-# huge amounts of memory, because the whole span would be read at once,
-# including all the intermediate revisions that aren't pertinent for the chain.
-# This is why once a repository has enabled sparse-read, it becomes required.
-SPARSEREVLOG_REQUIREMENT = b'sparserevlog'
-
-# A repository with the sidedataflag requirement will allow to store extra
-# information for revision without altering their original hashes.
-SIDEDATA_REQUIREMENT = b'exp-sidedata-flag'
-
-# A repository with the the copies-sidedata-changeset requirement will store
-# copies related information in changeset's sidedata.
-COPIESSDC_REQUIREMENT = b'exp-copies-sidedata-changeset'
-
-# The repository use persistent nodemap for the changelog and the manifest.
-NODEMAP_REQUIREMENT = b'persistent-nodemap'
-
 # Functions receiving (ui, features) that extensions can register to impact
 # the ability to load repositories with custom requirements. Only
 # functions defined in loaded extensions are called.
@@ -863,12 +839,15 @@
     # This revlog format is super old and we don't bother trying to parse
     # opener options for it because those options wouldn't do anything
     # meaningful on such old repos.
-    if b'revlogv1' in requirements or REVLOGV2_REQUIREMENT in requirements:
+    if (
+        b'revlogv1' in requirements
+        or requirementsmod.REVLOGV2_REQUIREMENT in requirements
+    ):
         options.update(resolverevlogstorevfsoptions(ui, requirements, features))
     else:  # explicitly mark repo as using revlogv0
         options[b'revlogv0'] = True
 
-    if COPIESSDC_REQUIREMENT in requirements:
+    if requirementsmod.COPIESSDC_REQUIREMENT in requirements:
         options[b'copies-storage'] = b'changeset-sidedata'
     else:
         writecopiesto = ui.config(b'experimental', b'copies.write-to')
@@ -887,7 +866,7 @@
 
     if b'revlogv1' in requirements:
         options[b'revlogv1'] = True
-    if REVLOGV2_REQUIREMENT in requirements:
+    if requirementsmod.REVLOGV2_REQUIREMENT in requirements:
         options[b'revlogv2'] = True
 
     if b'generaldelta' in requirements:
@@ -931,12 +910,12 @@
     options[b'sparse-read-density-threshold'] = srdensitythres
     options[b'sparse-read-min-gap-size'] = srmingapsize
 
-    sparserevlog = SPARSEREVLOG_REQUIREMENT in requirements
+    sparserevlog = requirementsmod.SPARSEREVLOG_REQUIREMENT in requirements
     options[b'sparse-revlog'] = sparserevlog
     if sparserevlog:
         options[b'generaldelta'] = True
 
-    sidedata = SIDEDATA_REQUIREMENT in requirements
+    sidedata = requirementsmod.SIDEDATA_REQUIREMENT in requirements
     options[b'side-data'] = sidedata
 
     maxchainlen = None
@@ -972,7 +951,7 @@
 
     if ui.configbool(b'experimental', b'rust.index'):
         options[b'rust.index'] = True
-    if NODEMAP_REQUIREMENT in requirements:
+    if requirementsmod.NODEMAP_REQUIREMENT in requirements:
         options[b'persistent-nodemap'] = True
     if ui.configbool(b'storage', b'revlog.nodemap.mmap'):
         options[b'persistent-nodemap.mmap'] = True
@@ -1058,11 +1037,11 @@
         b'revlogv1',
         b'generaldelta',
         requirementsmod.TREEMANIFEST_REQUIREMENT,
-        COPIESSDC_REQUIREMENT,
-        REVLOGV2_REQUIREMENT,
-        SIDEDATA_REQUIREMENT,
-        SPARSEREVLOG_REQUIREMENT,
-        NODEMAP_REQUIREMENT,
+        requirementsmod.COPIESSDC_REQUIREMENT,
+        requirementsmod.REVLOGV2_REQUIREMENT,
+        requirementsmod.SIDEDATA_REQUIREMENT,
+        requirementsmod.SPARSEREVLOG_REQUIREMENT,
+        requirementsmod.NODEMAP_REQUIREMENT,
         bookmarks.BOOKMARKS_IN_STORE_REQUIREMENT,
     }
     _basesupported = supportedformats | {
@@ -1241,7 +1220,7 @@
         self._extrafilterid = repoview.extrafilter(ui)
 
         self.filecopiesmode = None
-        if COPIESSDC_REQUIREMENT in self.requirements:
+        if requirementsmod.COPIESSDC_REQUIREMENT in self.requirements:
             self.filecopiesmode = b'changeset-sidedata'
 
     def _getvfsward(self, origfunc):
@@ -3308,15 +3287,15 @@
     if scmutil.gdinitconfig(ui):
         requirements.add(b'generaldelta')
         if ui.configbool(b'format', b'sparse-revlog'):
-            requirements.add(SPARSEREVLOG_REQUIREMENT)
+            requirements.add(requirementsmod.SPARSEREVLOG_REQUIREMENT)
 
     # experimental config: format.exp-use-side-data
     if ui.configbool(b'format', b'exp-use-side-data'):
-        requirements.add(SIDEDATA_REQUIREMENT)
+        requirements.add(requirementsmod.SIDEDATA_REQUIREMENT)
     # experimental config: format.exp-use-copies-side-data-changeset
     if ui.configbool(b'format', b'exp-use-copies-side-data-changeset'):
-        requirements.add(SIDEDATA_REQUIREMENT)
-        requirements.add(COPIESSDC_REQUIREMENT)
+        requirements.add(requirementsmod.SIDEDATA_REQUIREMENT)
+        requirements.add(requirementsmod.COPIESSDC_REQUIREMENT)
     if ui.configbool(b'experimental', b'treemanifest'):
         requirements.add(requirementsmod.TREEMANIFEST_REQUIREMENT)
 
@@ -3325,7 +3304,7 @@
         requirements.remove(b'revlogv1')
         # generaldelta is implied by revlogv2.
         requirements.discard(b'generaldelta')
-        requirements.add(REVLOGV2_REQUIREMENT)
+        requirements.add(requirementsmod.REVLOGV2_REQUIREMENT)
     # experimental config: format.internal-phase
     if ui.configbool(b'format', b'internal-phase'):
         requirements.add(requirementsmod.INTERNAL_PHASE_REQUIREMENT)
@@ -3340,7 +3319,7 @@
         requirements.add(bookmarks.BOOKMARKS_IN_STORE_REQUIREMENT)
 
     if ui.configbool(b'format', b'use-persistent-nodemap'):
-        requirements.add(NODEMAP_REQUIREMENT)
+        requirements.add(requirementsmod.NODEMAP_REQUIREMENT)
 
     return requirements
 

--- a/mercurial/requirements.py	Sat Aug 08 16:24:12 2020 +0530
+++ b/mercurial/requirements.py	Sat Aug 08 16:37:59 2020 +0530
@@ -20,3 +20,27 @@
 
 # Stores manifest in Tree structure
 TREEMANIFEST_REQUIREMENT = b'treemanifest'
+
+# Increment the sub-version when the revlog v2 format changes to lock out old
+# clients.
+REVLOGV2_REQUIREMENT = b'exp-revlogv2.1'
+
+# A repository with the sparserevlog feature will have delta chains that
+# can spread over a larger span. Sparse reading cuts these large spans into
+# pieces, so that each piece isn't too big.
+# Without the sparserevlog capability, reading from the repository could use
+# huge amounts of memory, because the whole span would be read at once,
+# including all the intermediate revisions that aren't pertinent for the chain.
+# This is why once a repository has enabled sparse-read, it becomes required.
+SPARSEREVLOG_REQUIREMENT = b'sparserevlog'
+
+# A repository with the sidedataflag requirement will allow to store extra
+# information for revision without altering their original hashes.
+SIDEDATA_REQUIREMENT = b'exp-sidedata-flag'
+
+# A repository with the the copies-sidedata-changeset requirement will store
+# copies related information in changeset's sidedata.
+COPIESSDC_REQUIREMENT = b'exp-copies-sidedata-changeset'
+
+# The repository use persistent nodemap for the changelog and the manifest.
+NODEMAP_REQUIREMENT = b'persistent-nodemap'

--- a/mercurial/upgrade.py	Sat Aug 08 16:24:12 2020 +0530
+++ b/mercurial/upgrade.py	Sat Aug 08 16:37:59 2020 +0530
@@ -32,7 +32,7 @@
 # list of requirements that request a clone of all revlog if added/removed
 RECLONES_REQUIREMENTS = {
     b'generaldelta',
-    localrepo.SPARSEREVLOG_REQUIREMENT,
+    requirements.SPARSEREVLOG_REQUIREMENT,
 }
 
 
@@ -76,10 +76,10 @@
     to be allowed.
     """
     supported = {
-        localrepo.SPARSEREVLOG_REQUIREMENT,
-        localrepo.SIDEDATA_REQUIREMENT,
-        localrepo.COPIESSDC_REQUIREMENT,
-        localrepo.NODEMAP_REQUIREMENT,
+        requirements.SPARSEREVLOG_REQUIREMENT,
+        requirements.SIDEDATA_REQUIREMENT,
+        requirements.COPIESSDC_REQUIREMENT,
+        requirements.NODEMAP_REQUIREMENT,
     }
     for name in compression.compengines:
         engine = compression.compengines[name]
@@ -104,10 +104,10 @@
         b'generaldelta',
         b'revlogv1',
         b'store',
-        localrepo.SPARSEREVLOG_REQUIREMENT,
-        localrepo.SIDEDATA_REQUIREMENT,
-        localrepo.COPIESSDC_REQUIREMENT,
-        localrepo.NODEMAP_REQUIREMENT,
+        requirements.SPARSEREVLOG_REQUIREMENT,
+        requirements.SIDEDATA_REQUIREMENT,
+        requirements.COPIESSDC_REQUIREMENT,
+        requirements.NODEMAP_REQUIREMENT,
     }
     for name in compression.compengines:
         engine = compression.compengines[name]
@@ -132,10 +132,10 @@
         b'dotencode',
         b'fncache',
         b'generaldelta',
-        localrepo.SPARSEREVLOG_REQUIREMENT,
-        localrepo.SIDEDATA_REQUIREMENT,
-        localrepo.COPIESSDC_REQUIREMENT,
-        localrepo.NODEMAP_REQUIREMENT,
+        requirements.SPARSEREVLOG_REQUIREMENT,
+        requirements.SIDEDATA_REQUIREMENT,
+        requirements.COPIESSDC_REQUIREMENT,
+        requirements.NODEMAP_REQUIREMENT,
     }
     for name in compression.compengines:
         engine = compression.compengines[name]
@@ -339,7 +339,7 @@
 class sparserevlog(requirementformatvariant):
     name = b'sparserevlog'
 
-    _requirement = localrepo.SPARSEREVLOG_REQUIREMENT
+    _requirement = requirements.SPARSEREVLOG_REQUIREMENT
 
     default = True
 
@@ -365,7 +365,7 @@
 class sidedata(requirementformatvariant):
     name = b'sidedata'
 
-    _requirement = localrepo.SIDEDATA_REQUIREMENT
+    _requirement = requirements.SIDEDATA_REQUIREMENT
 
     default = False
 
@@ -381,7 +381,7 @@
 class persistentnodemap(requirementformatvariant):
     name = b'persistent-nodemap'
 
-    _requirement = localrepo.NODEMAP_REQUIREMENT
+    _requirement = requirements.NODEMAP_REQUIREMENT
 
     default = False
 
@@ -396,7 +396,7 @@
 class copiessdc(requirementformatvariant):
     name = b'copies-sdc'
 
-    _requirement = localrepo.COPIESSDC_REQUIREMENT
+    _requirement = requirements.COPIESSDC_REQUIREMENT
 
     default = False
 
@@ -726,7 +726,7 @@
     sidedatacompanion = None
     removedreqs = srcrepo.requirements - dstrepo.requirements
     addedreqs = dstrepo.requirements - srcrepo.requirements
-    if localrepo.SIDEDATA_REQUIREMENT in removedreqs:
+    if requirements.SIDEDATA_REQUIREMENT in removedreqs:
 
         def sidedatacompanion(rl, rev):
             rl = getattr(rl, '_revlog', rl)
@@ -734,9 +734,9 @@
                 return True, (), {}
             return False, (), {}
 
-    elif localrepo.COPIESSDC_REQUIREMENT in addedreqs:
+    elif requirements.COPIESSDC_REQUIREMENT in addedreqs:
         sidedatacompanion = metadata.getsidedataadder(srcrepo, dstrepo)
-    elif localrepo.COPIESSDC_REQUIREMENT in removedreqs:
+    elif requirements.COPIESSDC_REQUIREMENT in removedreqs:
         sidedatacompanion = metadata.getsidedataremover(srcrepo, dstrepo)
     return sidedatacompanion
 

--- a/tests/testlib/ext-sidedata.py	Sat Aug 08 16:24:12 2020 +0530
+++ b/tests/testlib/ext-sidedata.py	Sat Aug 08 16:37:59 2020 +0530
@@ -12,8 +12,8 @@
 
 from mercurial import (
     extensions,
-    localrepo,
     node,
+    requirements,
     revlog,
     upgrade,
 )
@@ -54,7 +54,7 @@
 def wrapgetsidedatacompanion(orig, srcrepo, dstrepo):
     sidedatacompanion = orig(srcrepo, dstrepo)
     addedreqs = dstrepo.requirements - srcrepo.requirements
-    if localrepo.SIDEDATA_REQUIREMENT in addedreqs:
+    if requirements.SIDEDATA_REQUIREMENT in addedreqs:
         assert sidedatacompanion is None  # deal with composition later
 
         def sidedatacompanion(revlog, rev):