commands: add postincoming explicit brev argument (API)
Before this patch, postincoming() initializes 'brev' with 'checkout',
but this isn't useful to activate/deactivate bookmark after updating,
because 'checkout' is not a string actually specified at command line,
but an already node-nized byte sequence.
This patch adds postincoming() explicit 'brev' argument, and makes
'pull()' pass appropriate value.
This patch adds 'brev' argument instead of 'brev=None', because
'brev=None' isn't reasonable value if checkout is not None.
Hello, Foobar
['Hello, Fo, =;:<o', 'Hello, Bar']