tests/test-rebase-partial.t

sparse: move code for importing rules from files into core

This is a pretty straightforward port. Some code cleanup was
performed. But no major changes to the logic were made.

I'm not a huge fan of this function because it does multiple
things. I'd like to get things into core first to facilitate
refactoring later.

Please also note the added inline comment about the oddities
of writeconfig() and the try..except to undo it. This is because
of the hackiness in which the sparse matcher is obtained by
various consumers, notably dirstate. We'll need a massive
refactor to address this. That refactor is effectively blocked
on having the sparse dirstate hacks live in core.

Tests rebasing with part of the rebase set already in the
destination (issue5422)

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > drawdag=$TESTDIR/drawdag.py
  > 
  > [experimental]
  > evolution=createmarkers,allowunstable
  > 
  > [alias]
  > tglog = log -G --template "{rev}: {desc}"
  > EOF

  $ rebasewithdag() {
  >   N=`$PYTHON -c "print($N+1)"`
  >   hg init repo$N && cd repo$N
  >   hg debugdrawdag
  >   hg rebase "$@" > _rebasetmp
  >   r=$?
  >   grep -v 'saved backup bundle' _rebasetmp
  >   [ $r -eq 0 ] && hg tglog
  >   cd ..
  >   return $r
  > }

Rebase two commits, of which one is already in the right place

  $ rebasewithdag -r C+D -d B <<EOF
  > C
  > |
  > B D
  > |/
  > A
  > EOF
  rebasing 2:b18e25de2cf5 "D" (D)
  already rebased 3:26805aba1e60 "C" (C tip)
  o  4: D
  |
  | o  3: C
  |/
  | x  2: D
  | |
  o |  1: B
  |/
  o  0: A
  
Can collapse commits even if one is already in the right place

  $ rebasewithdag --collapse -r C+D -d B <<EOF
  > C
  > |
  > B D
  > |/
  > A
  > EOF
  rebasing 2:b18e25de2cf5 "D" (D)
  rebasing 3:26805aba1e60 "C" (C tip)
  o  4: Collapsed revision
  |  * D
  |  * C
  | x  3: C
  |/
  | x  2: D
  | |
  o |  1: B
  |/
  o  0: A
  
Rebase with "holes". The commits after the hole should end up on the parent of
the hole (B below), not on top of the destination (A).

  $ rebasewithdag -r B+D -d A <<EOF
  > D
  > |
  > C
  > |
  > B
  > |
  > A
  > EOF
  already rebased 1:112478962961 "B" (B)
  not rebasing ignored 2:26805aba1e60 "C" (C)
  rebasing 3:f585351a92f8 "D" (D tip)
  o  4: D
  |
  | x  3: D
  | |
  | o  2: C
  |/
  o  1: B
  |
  o  0: A