narrow: check for servers' narrow support before doing anything (BC)
Recently we introduced narrow capabilities for the server. So we can check
whether a server has narrow clone support or not before doing anything. This is
BC because new clients won't be able to extend from old narrow-enabled servers.
I *think* narrow is not used much (maybe just inside Google), also it's
experimental so I think we can change this. We will need to this someday anyway.
The "doesn't" in error is changed to "does not" because I think that's we do in
core. I also changed one more instance of the error message to use 'does not'
for consistency.
Differential Revision: https://phab.mercurial-scm.org/D4789
node = <module 'mercurial.node' from '?'>
errorproxy = <unloaded module 'error'>
errorproxy.__doc__ = 'Mercurial exceptions. This ...'
errorproxy.__name__ = 'mercurial.error'
errorproxy.__dict__['__name__'] = 'mercurial.error'
errorproxy = <proxied module 'error'>
os = <unloaded module 'os'>
os.system = <built-in function system>
os = <module 'os' from '?'>
procutil = <unloaded module 'procutil'>
procutil.system = <function system at 0x?>
procutil = <module 'mercurial.utils.procutil' from '?'>
procutil.system = <function system at 0x?>
hgweb = <unloaded module 'hgweb'>
hgweb_mod = <unloaded module 'hgweb_mod'>
hgweb = <module 'mercurial.hgweb' from '?'>
fred = <unloaded module 're'>
remod = <unloaded module 're'>
re = <unloaded module 'sys'>
fred = <unloaded module 're'>
fred.sub = <function sub at 0x?>
fred = <proxied module 're'>
remod = <module 're' from '?'>
re = <unloaded module 'sys'>
re.stderr = <open file '<whatever>', mode 'w' at 0x?>
re = <proxied module 'sys'>
contextlib = <unloaded module 'contextlib'>
contextlib.unknownattr = ImportError: cannot import name unknownattr
__import__('contextlib', ..., ['unknownattr']) = <module 'contextlib' from '?'>
hasattr(contextlibimp, 'unknownattr') = False