exchange: support defining narrow file patterns for pull
This commit teaches exchange.pull() about the desire to perform a
narrow file pull. We simply pass include and exclude patterns to
the function. The values are validated and stored on the pulloperation
instance.
hg.clone() has been taught to pass these arguments to exchange.pull().
If the arguments are not passed to exchange.pull(), the active narrow
patterns from the repository will automatically be used. We /could/
always use the narrow patterns from the repo. However, allowing
explicit values to be passed in allows us to perform data fetching
that doesn't necessarily align with the repo configuration. This
provides more flexibility.
Differential Revision: https://phab.mercurial-scm.org/D4539
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