Infer a --repository argument from command arguments when reasonable.
In particular: if invoked without -R from a CWD not inside a repo, having been
passed one or more file paths as command arguments, where the nearest enclosing
repo of all of those paths is the same, quietly infer a -R option for that repo.
Otherwise abort with an error message as before.
hgweb: separate protocol calls from interface calls (
issue996)
The protocol functions are already pretty careful about not raising
exceptions to the caller, and have their own error handling. We can formalize
this a little bit to make it clearer (before, the exception handlers for
a limited number of exceptions coming from the interface bits would blow up
because some variables aren't instantiated for the protocol calls).