tests: add extension to emulate invoking dirstate.write at the specific time
This extension fakes 'now' for 'parsers.pack_dirstate()' to emulate
invoking 'dirstate.write()' at the specific time, only when
'dirstate.write()' is invoked via functions below:
- 'workingctx._checklookup()' (= 'repo.status()')
- 'committablectx.markcommitted()'
This is useful to reproduce timing critical issues fixed in subsequent
patches.
os = <unloaded module 'os'>
os.system = <built-in function system>
os = <module 'os' from '?'>
util = <unloaded module 'util'>
util.system = <function system at 0x?>
util = <module 'mercurial.util' from '?'>
util.system = <function system at 0x?>
fred = <unloaded module 're'>
re = <unloaded module 'sys'>
fred = <unloaded module 're'>
fred.sub = <function sub at 0x?>
fred = <proxied module 're'>
re = <unloaded module 'sys'>
re.stderr = <open file '<whatever>', mode 'w' at 0x?>
re = <proxied module 'sys'>
node = <module 'mercurial.node' from '?'>