convert: refactor sink initialisation, to remove hardcoding of hg We also introduce options to explicitly set the source and destination repository types. Improve testing of corner cases a little.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m test -d "1000000 0"
hg history
hg manifest --debug
hg cat a
hg verify