mq: initializing patchheader class directly from patch content
The patch header needs only be read in order to instantiate the class,
and as such it makes more sense to do it within the class.
#!/bin/sh
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i