lfs: infer the blob store URL from an explicit push dest or default-push
Unlike pull, the blobs are uploaded within the exchange.push() window, so simply
wrap it and swap in a properly configured remote store. The '_subtoppath' field
shouldn't be available during this window, but give the passed path priority for
clarity.
At one point I hit an AttributeError in one of the convert tests when trying to
save the original remote blobstore when the swap was run unconditionally. I
wrapped it in a util.safehasattr(), but then today I wasn't able to reproduce
it. But now the whole thing is tucked under the requirement guard because
without the requirement, there are no blobs in the repo, even if the extension
is loaded.
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 '?'>
util = <unloaded module 'util'>
util.system = <function system at 0x?>
util = <module 'mercurial.util' from '?'>
util.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