repository: introduce constant for internal phase repo requirement and use it

In future we will like to much cleaner logic around which requirement is for
working copy and which can go in store. To start with that, we first need to
de-clutter the requirement values spread around and replace them with constants.

Differential Revision: https://phab.mercurial-scm.org/D8912

mercurial/interfaces/repository.py

@@ -18,6 +18,10 b" NARROW_REQUIREMENT = b'narrowhg-experime"
 # Enables sparse working directory usage
 SPARSE_REQUIREMENT = b'exp-sparse'
 
+# Enables the internal phase which is used to hide changesets instead
+# of stripping them
+INTERNAL_PHASE_REQUIREMENT = b'internal-phase'
+
 # Local repository feature string.
 
 # Revlogs are being used for file storage.

mercurial/localrepo.py

@@ -1068,7 +1068,7 b' class localrepository(object):'
         b'relshared',
         b'dotencode',
         repository.SPARSE_REQUIREMENT,
-        b'internal-phase',
+        repository.INTERNAL_PHASE_REQUIREMENT,
     }
 
     # list of prefix for file which can be written without 'wlock'
@@ -3324,7 +3324,7 b' def newreporequirements(ui, createopts):'
         requirements.add(REVLOGV2_REQUIREMENT)
     # experimental config: format.internal-phase
     if ui.configbool(b'format', b'internal-phase'):
-        requirements.add(b'internal-phase')
+        requirements.add(repository.INTERNAL_PHASE_REQUIREMENT)
 
     if createopts.get(b'narrowfiles'):
         requirements.add(repository.NARROW_REQUIREMENT)

mercurial/phases.py

@@ -125,6 +125,7 b' from . import ('
     txnutil,
     util,
 )
+from .interfaces import repository
 
 _fphasesentry = struct.Struct(b'>i20s')
 
@@ -154,7 +155,7 b' localhiddenphases = (internal, archived)'
 
 def supportinternal(repo):
     """True if the internal phase can be used on a repository"""
-    return b'internal-phase' in repo.requirements
+    return repository.INTERNAL_PHASE_REQUIREMENT in repo.requirements
 
 
 def _readroots(repo, phasedefaults=None):