23 

    24 # Increment the sub-version when the revlog v2 format changes to lock out old

    25 # clients.

    26 REVLOGV2_REQUIREMENT = b'exp-revlogv2.1'

    27 

    28 # A repository with the sparserevlog feature will have delta chains that

    29 # can spread over a larger span. Sparse reading cuts these large spans into

    30 # pieces, so that each piece isn't too big.

    31 # Without the sparserevlog capability, reading from the repository could use

    32 # huge amounts of memory, because the whole span would be read at once,

    33 # including all the intermediate revisions that aren't pertinent for the chain.

    34 # This is why once a repository has enabled sparse-read, it becomes required.

    35 SPARSEREVLOG_REQUIREMENT = b'sparserevlog'

    36 

    37 # A repository with the sidedataflag requirement will allow to store extra

    38 # information for revision without altering their original hashes.

    39 SIDEDATA_REQUIREMENT = b'exp-sidedata-flag'

    40 

    41 # A repository with the the copies-sidedata-changeset requirement will store

    42 # copies related information in changeset's sidedata.

    43 COPIESSDC_REQUIREMENT = b'exp-copies-sidedata-changeset'

    44 

    45 # The repository use persistent nodemap for the changelog and the manifest.

    46 NODEMAP_REQUIREMENT = b'persistent-nodemap'