requirements: introduce a set of working directory specific requirements

Some requirements like the SPARSE_REQUIREMENT is working directory specific and
cannot be shared. We add a set which will contain all these requirements.

This is not the best we can do, I think having a rich requirement class will be
much better but that will be out of scope for this series.

Differential Revision: https://phab.mercurial-scm.org/D8924

mercurial/requirements.py

@@ -1,46 +1,51 b''
 # requirements.py - objects and functions related to repository requirements
 #
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 # When narrowing is finalized and no longer subject to format changes,
 # we should move this to just "narrow" or similar.
 NARROW_REQUIREMENT = b'narrowhg-experimental'
 
 # 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'
 
 # 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'
+
+# List of requirements which are working directory specific
+# These requirements cannot be shared between repositories if they
+# share the same store
+WORKING_DIR_REQUIREMENTS = {SPARSE_REQUIREMENT}