convert: make contents of "extra" dict available from sources, for sinks. This breaks hash preservation for hg->hg conversion, as each converted change gets a convert_revision item added to its extra dict. Ugh.

#!/bin/sh

hg init
echo a > a
hg ci -Am t

hg mv a b
hg ci -Am t1
hg debugrename b

hg mv b a
hg ci -Am t2
hg debugrename a

echo % test with --rev
hg debugrename --rev 1 b