view tests/test-issue672.t @ 35058:a68c3420be41

rebase: exclude descendants of obsoletes w/o a successor in dest (issue5300)

.. feature::

   Let 'hg rebase' avoid content-divergence by skipping obsolete
   changesets (and their descendants) when they are present in the rebase
   set along with one of their successors but none of their successors is
   in destination.

In the following example, when trying to rebase 3:: onto 2, the rebase
will abort with "this rebase will cause divergence from: 4":

    o  7 f
    |
    | o  6 e
    | |
    | o  5 d'
    | |
    x |  4 d (rewritten as 5)
    |/
    o  3 c
    |
    | o  2 x
    | |
    o |  1 b
    |/
    o  0 a

By excluding obsolete changesets without a successor in destination (4
in the example above) and their descendants, we make rebase work in this
case, thus giving:

    o  11 e
    |
    o  10 d'
    |
    o  9 c
    |
    o  8 b
    |
    | o  7 f
    | |
    | | x  6 e (rewritten using rebase as 11)
    | | |
    | | x  5 d' (rewritten using rebase as 10)
    | | |
    | x |  4 d
    | |/
    | x  3 c (rewritten using rebase as 9)
    | |
    o |  2 x
    | |
    | x  1 b (rewritten using rebase as 8)
    |/
    o  0 a

where branch 4:: is left behind while branch 5:: is rebased as expected.

The rationale is that users may not be interested in rebasing orphan
changesets when specifying a rebase set that include them but would
still want "stable" ones to be rebased. Currently, the user is suggested
to allow divergence (but probably does not want it) or they must specify
a rebase set excluding problematic changesets (which might be a bit
cumbersome). The approach proposed here corresponds to "Option 2" in
https://www.mercurial-scm.org/wiki/CEDRebase.


We extend _computeobsoletenotrebased() so that it also return a set of
obsolete changesets in rebase set without a successor in destination but
with at least one successor in rebase set. This
'obsoletewithoutsuccessorindestination' is then stored as an attribute
of rebaseruntime and used in _performrebasesubset() to:

* filter out descendants of these changesets from the revisions to
  rebase;
* issue a message about these revisions being skipped.

This only occurs if 'evolution.allowdivergence' option is off and
'rebaseskipobsolete' is on.

https://bz.mercurial-scm.org/672

# 0-2-4
#  \ \ \
#   1-3-5
#
# rename in #1, content change in #4.

  $ hg init

  $ touch 1
  $ touch 2
  $ hg commit -Am init  # 0
  adding 1
  adding 2

  $ hg rename 1 1a
  $ hg commit -m rename # 1

  $ hg co -C 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo unrelated >> 2
  $ hg ci -m unrelated1 # 2
  created new head

  $ hg merge --debug 1
    searching for copies back to rev 1
    unmatched files in other:
     1a
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: '1' -> dst: '1a' 
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 81f4b099af3d, local: c64f439569a9+, remote: c12dcd37c90a
   1: other deleted -> r
  removing 1
   1a: remote created -> g
  getting 1a
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg ci -m merge1 # 3

  $ hg co -C 2
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo hello >> 1
  $ hg ci -m unrelated2 # 4
  created new head

  $ hg co -C 3
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ hg merge -y --debug 4
    searching for copies back to rev 1
    unmatched files in local:
     1a
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: '1' -> dst: '1a' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c64f439569a9, local: e327dca35ac8+, remote: 746e9549ea96
   preserving 1a for resolve of 1a
  starting 4 threads for background file closing (?)
   1a: local copied/moved from 1 -> m (premerge)
  picked tool ':merge' for 1a (binary False symlink False changedelete False)
  merging 1a and 1 to 1a
  my 1a@e327dca35ac8+ other 1@746e9549ea96 ancestor 1@c64f439569a9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg co -C 4
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ hg merge -y --debug 3
    searching for copies back to rev 1
    unmatched files in other:
     1a
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: '1' -> dst: '1a' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c64f439569a9, local: 746e9549ea96+, remote: e327dca35ac8
   preserving 1 for resolve of 1a
  removing 1
  starting 4 threads for background file closing (?)
   1a: remote moved from 1 -> m (premerge)
  picked tool ':merge' for 1a (binary False symlink False changedelete False)
  merging 1 and 1a to 1a
  my 1a@746e9549ea96+ other 1a@e327dca35ac8 ancestor 1@c64f439569a9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)