#chg-compatible

  $ configure mutation
  $ setconfig extensions.bruterebase="$TESTDIR/bruterebase.py"
  $ init() {
  >   N=`expr ${N:-0} + 1`
  >   cd $TESTTMP && hg init repo$N && cd repo$N
  >   drawdag
  > }

Source looks like "N"

  $ init <<'EOS'
  > C D
  > |\|
  > A B Z
  > EOS

  $ hg debugbruterebase "all()-$Z" $Z --hidden
     A: A':Z
     B: B':Z
    AB: A':Z B':Z
     C: ABORT: cannot rebase a35c07e8a2a4 without moving at least one of its parents
    AC: A':Z C':A'B
    BC: B':Z C':B'A
   ABC: A':Z B':Z C':A'B'
     D: D':Z
    AD: A':Z D':Z
    BD: B':Z D':B'
   ABD: A':Z B':Z D':B'
    CD: ABORT: cannot rebase a35c07e8a2a4 without moving at least one of its parents
   ACD: A':Z C':A'B D':Z
   BCD: B':Z C':B'A D':B'
  ABCD: A':Z B':Z C':A'B' D':B'

Moving backwards

  $ init <<'EOS'
  > C
  > |\
  > A B
  > |
  > Z
  > EOS
  $ hg debugbruterebase "all()-$Z" $Z --hidden
    B: B':Z
    A: 
   BA: B':Z
    C: ABORT: cannot rebase b8d7149b562b without moving at least one of its parents
   BC: B':Z C':B'A
   AC: 
  BAC: B':Z C':B'A