repository: introduce constant for sparse repo requirement and use it

repository: introduce constant for sparse 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/D8911

--- a/mercurial/interfaces/repository.py	Fri Aug 07 16:02:13 2020 +0530
+++ b/mercurial/interfaces/repository.py	Sat Aug 08 10:06:32 2020 -0700
@@ -15,6 +15,9 @@
 # we should move this to just "narrow" or similar.
 NARROW_REQUIREMENT = b'narrowhg-experimental'
 
+# Enables sparse working directory usage
+SPARSE_REQUIREMENT = b'exp-sparse'
+
 # Local repository feature string.
 
 # Revlogs are being used for file storage.

--- a/mercurial/localrepo.py	Fri Aug 07 16:02:13 2020 +0530
+++ b/mercurial/localrepo.py	Sat Aug 08 10:06:32 2020 -0700
@@ -816,7 +816,7 @@
 
     ``error.RepoError`` should be raised on failure.
     """
-    if b'exp-sparse' in requirements and not sparse.enabled:
+    if repository.SPARSE_REQUIREMENT in requirements and not sparse.enabled:
         raise error.RepoError(
             _(
                 b'repository is using sparse feature but '
@@ -1067,7 +1067,7 @@
         b'shared',
         b'relshared',
         b'dotencode',
-        b'exp-sparse',
+        repository.SPARSE_REQUIREMENT,
         b'internal-phase',
     }
 

--- a/mercurial/sparse.py	Fri Aug 07 16:02:13 2020 +0530
+++ b/mercurial/sparse.py	Sat Aug 08 10:06:32 2020 -0700
@@ -24,8 +24,10 @@
     scmutil,
     util,
 )
+from .interfaces import repository
 from .utils import hashutil
 
+
 # Whether sparse features are enabled. This variable is intended to be
 # temporary to facilitate porting sparse to core. It should eventually be
 # a per-repo option, possibly a repo requirement.
@@ -606,11 +608,11 @@
     # updated. But this requires massive rework to matcher() and its
     # consumers.
 
-    if b'exp-sparse' in oldrequires and removing:
-        repo.requirements.discard(b'exp-sparse')
+    if repository.SPARSE_REQUIREMENT in oldrequires and removing:
+        repo.requirements.discard(repository.SPARSE_REQUIREMENT)
         scmutil.writereporequirements(repo)
-    elif b'exp-sparse' not in oldrequires:
-        repo.requirements.add(b'exp-sparse')
+    elif repository.SPARSE_REQUIREMENT not in oldrequires:
+        repo.requirements.add(repository.SPARSE_REQUIREMENT)
         scmutil.writereporequirements(repo)
 
     try: