cat: default to working dir parent instead of tip
This introduces a defaultrev function that chooses
the working dir parent if a revision isn't specified,
and uses it in several places.
adding base
abort: cannot delete applied patch c
Now at: b
a
b
a
b
series
status
Now at: a
a
b
series
status
1 New patch: a
0 base
abort: patch e not at base
f
4 New patch: f
3 New patch: e
2 New patch: d
1 New patch: a
0 base