mercurial/requirements.py

perf: ensure all readlog's reading is done within a `reading` context

We are about to enforce this at the revlog level, so we update the perf code in
advance.

# requirements.py - objects and functions related to repository requirements
#
# Copyright 2005-2007 Olivia 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.


# obsolete experimental requirements:
#  - manifestv2: An experimental new manifest format that allowed
#    for stem compression of long paths. Experiment ended up not
#    being successful (repository sizes went up due to worse delta
#    chains), and the code was deleted in 4.6.

GENERALDELTA_REQUIREMENT = b'generaldelta'
DOTENCODE_REQUIREMENT = b'dotencode'
STORE_REQUIREMENT = b'store'
FNCACHE_REQUIREMENT = b'fncache'

DIRSTATE_TRACKED_HINT_V1 = b'dirstate-tracked-key-v1'
DIRSTATE_V2_REQUIREMENT = b'dirstate-v2'

# 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-2'

# Enables the internal phase which is used to hide changesets instead
# of stripping them
ARCHIVED_PHASE_REQUIREMENT = b'exp-archived-phase'

# Stores manifest in Tree structure
TREEMANIFEST_REQUIREMENT = b'treemanifest'

REVLOGV1_REQUIREMENT = b'revlogv1'

# allow using ZSTD as compression engine for revlog content
REVLOG_COMPRESSION_ZSTD = b'revlog-compression-zstd'

# Increment the sub-version when the revlog v2 format changes to lock out old
# clients.
CHANGELOGV2_REQUIREMENT = b'exp-changelog-v2'

# Increment the sub-version when the revlog v2 format changes to lock out old
# clients.
REVLOGV2_REQUIREMENT = b'exp-revlogv2.2'

# 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 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'

# Denotes that the current repository is a share
SHARED_REQUIREMENT = b'shared'

# Denotes that current repository is a share and the shared source path is
# relative to the current repository root path
RELATIVE_SHARED_REQUIREMENT = b'relshared'

# A repository with share implemented safely. The repository has different
# store and working copy requirements i.e. both `.hg/requires` and
# `.hg/store/requires` are present.
SHARESAFE_REQUIREMENT = b'share-safe'

# Bookmarks must be stored in the `store` part of the repository and will be
# share accross shares
BOOKMARKS_IN_STORE_REQUIREMENT = b'bookmarksinstore'

# List of requirements which are working directory specific
# These requirements cannot be shared between repositories if they
# share the same store
# * sparse is a working directory specific functionality and hence working
#   directory specific requirement
# * SHARED_REQUIREMENT and RELATIVE_SHARED_REQUIREMENT are requirements which
#   represents that the current working copy/repository shares store of another
#   repo. Hence both of them should be stored in working copy
# * SHARESAFE_REQUIREMENT needs to be stored in working dir to mark that rest of
#   the requirements are stored in store's requires
# * DIRSTATE_V2_REQUIREMENT affects .hg/dirstate, of which there is one per
#   working directory.
WORKING_DIR_REQUIREMENTS = {
    SPARSE_REQUIREMENT,
    SHARED_REQUIREMENT,
    RELATIVE_SHARED_REQUIREMENT,
    SHARESAFE_REQUIREMENT,
    DIRSTATE_TRACKED_HINT_V1,
    DIRSTATE_V2_REQUIREMENT,
}

# List of requirement that impact "stream-clone" (and hardlink clone) and
# cannot be changed in such cases.
#
# requirements not in this list are safe to be altered during stream-clone.
#
# note: the list is currently inherited from previous code and miss some relevant requirement while containing some irrelevant ones.
STREAM_FIXED_REQUIREMENTS = {
    ARCHIVED_PHASE_REQUIREMENT,
    BOOKMARKS_IN_STORE_REQUIREMENT,
    CHANGELOGV2_REQUIREMENT,
    COPIESSDC_REQUIREMENT,
    GENERALDELTA_REQUIREMENT,
    INTERNAL_PHASE_REQUIREMENT,
    REVLOG_COMPRESSION_ZSTD,
    REVLOGV1_REQUIREMENT,
    REVLOGV2_REQUIREMENT,
    SPARSEREVLOG_REQUIREMENT,
    TREEMANIFEST_REQUIREMENT,
}