nodemap: gate the feature behind a new requirement
Now that the feature is working smoothly, a question was still open, should we
gate the feature behind a new requirement or just treat it as a cache to be
warmed by those who can and ignored by other.
The advantage of using the cache approach is a transparent upgrade/downgrade
story, making the feature easier to move to. However having out of date cache
can come with a significant performance hit for process who expect an up to
date cache but found none. In this case the file needs to be stored under
`.hg/cache`.
The "requirement" approach guarantee that the persistent nodemap is up to date.
However, it comes with a less flexible activation story since an explicite
upgrade is required. In this case the file can be stored in `.hg/store`.
This wiki page is relevant to this questions:
https://www.mercurial-scm.org/wiki/ComputedIndexPlan
So which one should we take? Another element came into plan, the persistent
nodemap use the `add` method of the transaction, it is used to keep track of a
file content before a transaction in case we need to rollback it back. It turns
out that the `transaction.add` API does not support file stored anywhere than
`.hg/store`. Making it support file stored elsewhere is possible, require a
change in on disk transaction format. Updating on disk file requires…
introducing a new requirements.
As a result, we pick the second option "gating the persistent nodemap behind a
new requirements".
Differential Revision: https://phab.mercurial-scm.org/D8417
#!/usr/bin/env python
from __future__ import absolute_import
import getopt
import sys
import hgdemandimport
hgdemandimport.enable()
from mercurial.i18n import _
from mercurial import (
context,
error,
fancyopts,
pycompat,
simplemerge,
ui as uimod,
)
from mercurial.utils import procutil, stringutil
options = [
(b'L', b'label', [], _(b'labels to use on conflict markers')),
(b'a', b'text', None, _(b'treat all files as text')),
(b'p', b'print', None, _(b'print results instead of overwriting LOCAL')),
(b'', b'no-minimal', None, _(b'no effect (DEPRECATED)')),
(b'h', b'help', None, _(b'display help and exit')),
(b'q', b'quiet', None, _(b'suppress output')),
]
usage = _(
b'''simplemerge [OPTS] LOCAL BASE OTHER
Simple three-way file merge utility with a minimal feature set.
Apply to LOCAL the changes necessary to go from BASE to OTHER.
By default, LOCAL is overwritten with the results of this operation.
'''
)
class ParseError(Exception):
"""Exception raised on errors in parsing the command line."""
def showhelp():
pycompat.stdout.write(usage)
pycompat.stdout.write(b'\noptions:\n')
out_opts = []
for shortopt, longopt, default, desc in options:
out_opts.append(
(
b'%2s%s'
% (
shortopt and b'-%s' % shortopt,
longopt and b' --%s' % longopt,
),
b'%s' % desc,
)
)
opts_len = max([len(opt[0]) for opt in out_opts])
for first, second in out_opts:
pycompat.stdout.write(b' %-*s %s\n' % (opts_len, first, second))
try:
for fp in (sys.stdin, pycompat.stdout, sys.stderr):
procutil.setbinary(fp)
opts = {}
try:
bargv = [a.encode('utf8') for a in sys.argv[1:]]
args = fancyopts.fancyopts(bargv, options, opts)
except getopt.GetoptError as e:
raise ParseError(e)
if opts[b'help']:
showhelp()
sys.exit(0)
if len(args) != 3:
raise ParseError(_(b'wrong number of arguments').decode('utf8'))
local, base, other = args
sys.exit(
simplemerge.simplemerge(
uimod.ui.load(),
context.arbitraryfilectx(local),
context.arbitraryfilectx(base),
context.arbitraryfilectx(other),
**pycompat.strkwargs(opts)
)
)
except ParseError as e:
e = stringutil.forcebytestr(e)
pycompat.stdout.write(b"%s: %s\n" % (sys.argv[0].encode('utf8'), e))
showhelp()
sys.exit(1)
except error.Abort as e:
pycompat.stderr.write(b"abort: %s\n" % e)
sys.exit(255)
except KeyboardInterrupt:
sys.exit(255)