dispatch: parse and apply -R early
This allows us to use extensions specified in .hg/hgrc. Unfortunately,
this requires us to parse that file twice, but performance impact on
the version command appears to be less than 1%.
#!/bin/sh
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "1000000 0"
ls
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "1000000 0"
hg co 0
# B should disappear
ls