tests/test-rebase-brute-force.t

wireprotoserver: ability to run an SSH server until an event is set

It seems useful to be able to start an SSH protocol server that
won't run forever and won't call sys.exit() when it stops. This
could be used to facilitate intra-process testing of the SSH
protocol, for example.

We teach the server function to loop until a threading.Event is set
and invent a new API to run the server until an event is set. It also
won't sys.exit() afterwards.

There aren't many callers of serve_forever(). So we could refactor
them relatively easily. But I was lazy.

threading.Event might be a bit heavyweight. An alternative would be
a list whose only elements is changed. We can't use a simple scalar
value like a bool or int because those types are immutable. Events
are what you use in systems programming for this use case, so the
use of threading.Event seems justified.

Differential Revision: https://phab.mercurial-scm.org/D2461

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > drawdag=$TESTDIR/drawdag.py
  > bruterebase=$TESTDIR/bruterebase.py
  > [experimental]
  > evolution.createmarkers=True
  > evolution.allowunstable=True
  > EOF
  $ init() {
  >   N=`expr ${N:-0} + 1`
  >   cd $TESTTMP && hg init repo$N && cd repo$N
  >   hg debugdrawdag
  > }

Source looks like "N"

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

  $ hg debugbruterebase 'all()-Z' Z
     A: A':Z
     B: B':Z
    AB: A':Z B':Z
     C: ABORT: cannot rebase 3: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 3: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
    B: B':Z
    A: 
   BA: B':Z
    C: ABORT: cannot rebase 3:b8d7149b562b without moving at least one of its parents
   BC: B':Z C':B'A
   AC: 
  BAC: B':Z C':B'A