Mercurial > hg
view mercurial/txnutil.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.
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
---|---|
date | Wed, 27 Mar 2019 18:27:03 +0100 |
parents | 206532700213 |
children | 2372284d9457 |
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# txnutil.py - transaction related utilities # # Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others # # 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 import errno from . import ( encoding, ) def mayhavepending(root): '''return whether 'root' may have pending changes, which are visible to this process. ''' return root == encoding.environ.get('HG_PENDING') def trypending(root, vfs, filename, **kwargs): '''Open file to be read according to HG_PENDING environment variable This opens '.pending' of specified 'filename' only when HG_PENDING is equal to 'root'. This returns '(fp, is_pending_opened)' tuple. ''' if mayhavepending(root): try: return (vfs('%s.pending' % filename, **kwargs), True) except IOError as inst: if inst.errno != errno.ENOENT: raise return (vfs(filename, **kwargs), False)