Fix how setup.py identifies the Mercurial version.
There is a problem with setup.py where it will not identify the Mercurial
version properly when not being ran in within a repository even if
mercurial/__version__.py exists.
To fix, use mercurial.__version__.version when available before defaulting
to "unknown". (Using mercurial.util.version() is not an option due to a
dependency issue where osutil can be referenced before it is built.)
#!/bin/sh
mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m test -d "1000000 0"
rm .hg/requires
hg tip
echo indoor-pool > .hg/requires
hg tip
true