tests/test-basic.t

rebase: don't rebase obsolete commit whose successor is already rebased

This patch avoids unnecessary conflicts to resolve during rebase for the users
of changeset evolution.

This patch modifies rebase to skip obsolete commits if they are being rebased on
their successors.
It introduces a new rebase state 'revprecursor' for these revisions that are
being skipped and a new message to inform the user of what is happening.
This feature is gated behind the config flag experimental.rebaseskipobsolete

When an obsolete commit is skipped, the output is:
not rebasing 14:9ad579b4a5de "I", already in destination as 17:fc37a630c901 "K"

Create a repository:

  $ hg config
  defaults.backout=-d "0 0"
  defaults.commit=-d "0 0"
  defaults.shelve=--date "0 0"
  defaults.tag=-d "0 0"
  devel.all-warnings=true
  largefiles.usercache=$TESTTMP/.cache/largefiles (glob)
  ui.slash=True
  ui.interactive=False
  ui.mergemarkers=detailed
  ui.promptecho=True
  $ hg init t
  $ cd t

Make a changeset:

  $ echo a > a
  $ hg add a
  $ hg commit -m test

This command is ancient:

  $ hg history
  changeset:   0:acb14030fe0a
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     test
  

Verify that updating to revision 0 via commands.update() works properly

  $ cat <<EOF > update_to_rev0.py
  > from mercurial import ui, hg, commands
  > myui = ui.ui()
  > repo = hg.repository(myui, path='.')
  > commands.update(myui, repo, rev=0)
  > EOF
  $ hg up null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ python ./update_to_rev0.py
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg identify -n
  0


Poke around at hashes:

  $ hg manifest --debug
  b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644   a

  $ hg cat a
  a

Verify should succeed:

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 1 changesets, 1 total revisions

At the end...

  $ cd ..