transaction: clarify the "quick abort" scenario
Right now, the transaction has a code-pass to do a "quick abort" that skip most¹
(too much) of the logic when the right condition are detected²
We are about to improve this logic in multiple aspect. We clarify the code
first.
The conditional return in `_can_quick_abort` looks a bit weird because we are
about to make them more complex very soon.
[1] actually too much
[2] actually not often enough
# 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 . import encoding
def mayhavepending(root):
"""return whether 'root' may have pending changes, which are
visible to this process.
"""
return root == encoding.environ.get(b'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(b'%s.pending' % filename, **kwargs), True)
except FileNotFoundError:
pass
return (vfs(filename, **kwargs), False)