comparison mercurial/upgrade.py @ 42136:10a6725dca6e

compression: introduce an official `zstd-revlog` requirement

This requirement supersedes `exp-compression-zstd`. However, we keep support for
the old requirement.

Strictly speaking, we do not need to add a new requirement, there are no logic
change making "new" repo incompatible with mercurial client using a version
that support `exp-compression-zstd`.

The choice to introduce a new requirement is motivated by the following:

* The previous requirement was explicitly "experimental". Using it by default
  could confuse users.

* adding support for a hypothetical third compression engine will requires new
  code, and will comes with its own requirement tool.

* We won't use it as the default for a while since I do not think we support
  zstd on all platform. I can imagine we'll gain another (unrelated but on my
  default) requirement by the time we turn this zstd by default.

42135:b970fece153d

    upgrademessage = _('revlog content will be recompressed with the new '
                       'algorithm.')

    @classmethod
    def fromrepo(cls, repo):
        for req in repo.requirements:
            if req.startswith('exp-compression-'):
                return req.split('-', 2)[2]
        return 'zlib'

    @classmethod
    def fromconfig(cls, repo):
        return repo.ui.config('format', 'revlog-compression')

42136:10a6725dca6e

    upgrademessage = _('revlog content will be recompressed with the new '
                       'algorithm.')

    @classmethod
    def fromrepo(cls, repo):
        # we allow multiple compression engine requirement to co-exist because
        # strickly speaking, revlog seems to support mixed compression style.
        #
        # The compression used for new entries will be "the last one"
        compression = 'zlib'
        for req in repo.requirements:
            prefix = req.startswith
            if prefix('revlog-compression-') or prefix('exp-compression-'):
                compression = req.split('-', 2)[2]
        return compression

    @classmethod
    def fromconfig(cls, repo):
        return repo.ui.config('format', 'revlog-compression')