[MERGE][#144421][#144300] Use write lock in log and status with '-r branch:URL'

[Ian Clatworthy]

Lukáš Lalinský wrote:
> This patch replaces lock_read with lock_write in log and status if the
> 'branch:' revision specifier is used. I realize it would be probably
> better to just get rid of the implicit fetching, but I think fixing the
> lock is good enough as an interim solution.

bb:tweak

A NEWS entry is needed. I also think the new blackbox tests need names
that reflect what they are testing (branch specifiers for those
operations) instead of the particular bug being fixed (*_write_lock).

Ian C.