tests/test-rebase-empty-successor.t

merge: introduce mergeresult.addfile() and use it

We want to use mergeresult object at more and more places instead of this
actions dict to simplify code and further add new APIs to mergeresult object.

This patch introduces `addfile()` which adds a new file to the internal actions
dict for now.

Differential Revision: https://phab.mercurial-scm.org/D8820

  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > rebase=
  > [alias]
  > tglog = log -G -T "{rev} '{desc}'\n"
  > EOF

  $ hg init

  $ echo a > a; hg add a; hg ci -m a
  $ echo b > b; hg add b; hg ci -m b1
  $ hg up 0 -q
  $ echo b > b; hg add b; hg ci -m b2 -q

  $ hg tglog
  @  2 'b2'
  |
  | o  1 'b1'
  |/
  o  0 'a'
  

With rewrite.empty-successor=skip, b2 is skipped because it would become empty.

  $ hg rebase -s 2 -d 1 --config rewrite.empty-successor=skip --dry-run
  starting dry-run rebase; repository will not be changed
  rebasing 2:6e2aad5e0f3c "b2" (tip)
  note: not rebasing 2:6e2aad5e0f3c "b2" (tip), its destination already has all its changes
  dry-run rebase completed successfully; run without -n/--dry-run to perform this rebase

With rewrite.empty-successor=keep, b2 will be recreated although it became empty.

  $ hg rebase -s 2 -d 1 --config rewrite.empty-successor=keep
  rebasing 2:6e2aad5e0f3c "b2" (tip)
  note: created empty successor for 2:6e2aad5e0f3c "b2" (tip), its destination already has all its changes
  saved backup bundle to $TESTTMP/.hg/strip-backup/6e2aad5e0f3c-7d7c8801-rebase.hg

  $ hg tglog
  @  2 'b2'
  |
  o  1 'b1'
  |
  o  0 'a'