Anton Shestakov <av6@dwimlabs.net> [Thu, 07 Mar 2019 22:50:56 +0800] rev 4433
stack: optimize revset used for stack --children
Since that option needs to exclude changesets on the current stack, let's just
use stack.revs (that are cached) for that and skip branch() or topic() revset.
st.revs[0] is the stack base, we don't consider it actual part of stack.