view tests/test-rename-merge2.t @ 23702:c48924787eaa

filectx.parents: enforce changeid of parent to be in own changectx ancestors

Because of the way filenodes are computed, you can have multiple changesets
"introducing" the same file revision. For example, in the changeset graph
below, changeset 2 and 3 both change a file -to- and -from- the same content.

  o 3: content = new
  |
  | o 2: content = new
  |/
  o 1: content = old

In such cases, the file revision is create once, when 2 is added, and just reused
for 3. So the file change in '3' (from "old" to "new)" has no linkrev pointing
to it).  We'll call this situation "linkrev-shadowing". As the linkrev is used for
optimization purposes when walking a file history, the linkrev-shadowing
results in an unexpected jump to another branch during such a walk.. This leads to
multiple bugs with log, annotate and rename detection.

One element to fix such bugs is to ensure that walking the file history sticks on
the same topology as the changeset's history. For this purpose, we extend the
logic in 'basefilectx.parents' so that it always defines the proper changeset
to associate the parent file revision with. This "proper" changeset has to be an
ancestor of the changeset associated with the child file revision.

This logic is performed in the '_adjustlinkrev' function. This function is
given the starting changeset and all the information regarding the parent file
revision. If the linkrev for the file revision is an ancestor of the starting
changeset, the linkrev is valid and will be used. If it is not, we detected a
topological jump caused by linkrev shadowing, we are going to walk the
ancestors of the starting changeset until we find one setting the file to the
revision we are trying to create.

The performance impact appears acceptable:

- We are walking the changelog once for each filelog traversal (as there should
  be no overlap between searches),

- changelog traversal itself is fairly cheap, compared to what is likely going
  to be perform on the result on the filelog traversal,

- We only touch the manifest for ancestors touching the file, And such
  changesets are likely to be the one introducing the file. (except in
  pathological cases involving merge),

- We use manifest diff instead of full manifest unpacking to check manifest
  content, so it does not involve applying multiple diffs in most case.

- linkrev shadowing is not the common case.

Tests for fixed issues in log, annotate and rename detection have been
added.

But this changeset does not solve all problems. It fixes -ancestry-
computation, but if the linkrev-shadowed changesets is the starting one, we'll
still get things wrong. We'll have to fix the bootstrapping of such operations
in a later changeset. Also, the usage of `hg log FILE`  without --follow still
has issues with linkrev pointing to hidden changesets, because it relies on the
`filelog` revset which implement its own traversal logic that is still to be
fixed.

Thanks goes to:
- Matt Mackall: for nudging me in the right direction
- Julien Cristau and Rémi Cardona: for keep telling me linkrev bug were an
  evolution show stopper for 3 years.
- Durham Goode: for finding a new linkrev issue every few weeks
- Mads Kiilerich: for that last rename bug who raise this topic over my
  anoyance limit.

  $ mkdir -p t
  $ cd t
  $ cat <<EOF > merge
  > import sys, os
  > f = open(sys.argv[1], "wb")
  > f.write("merge %s %s %s" % (sys.argv[1], sys.argv[2], sys.argv[3]))
  > f.close()
  > EOF

perform a test merge with possible renaming
args:
$1 = action in local branch
$2 = action in remote branch
$3 = action in working dir
$4 = expected result

  $ tm()
  > {
  >     hg init t
  >     cd t
  >     echo "[merge]" >> .hg/hgrc
  >     echo "followcopies = 1" >> .hg/hgrc
  > 
  >     # base
  >     echo base > a
  >     echo base > rev # used to force commits
  >     hg add a rev
  >     hg ci -m "base"
  > 
  >     # remote
  >     echo remote > rev
  >     if [ "$2" != "" ] ; then $2 ; fi
  >     hg ci -m "remote"
  > 
  >     # local
  >     hg co -q 0
  >     echo local > rev
  >     if [ "$1" != "" ] ; then $1 ; fi
  >     hg ci -m "local"
  > 
  >     # working dir
  >     echo local > rev
  >     if [ "$3" != "" ] ; then $3 ; fi
  > 
  >     # merge
  >     echo "--------------"
  >     echo "test L:$1 R:$2 W:$3 - $4"
  >     echo "--------------"
  >     hg merge -y --debug --traceback --tool="python ../merge"
  > 
  >     echo "--------------"
  >     hg status -camC -X rev
  > 
  >     hg ci -m "merge"
  > 
  >     echo "--------------"
  >     echo
  > 
  >     cd ..
  >     rm -r t
  > }
  $ up() {
  >     cp rev $1
  >     hg add $1 2> /dev/null
  >     if [ "$2" != "" ] ; then
  >         cp rev $2
  >         hg add $2 2> /dev/null
  >     fi
  > }
  $ uc() { up $1; hg cp $1 $2; } # update + copy
  $ um() { up $1; hg mv $1 $2; }
  $ nc() { hg cp $1 $2; } # just copy
  $ nm() { hg mv $1 $2; } # just move
  $ tm "up a  " "nc a b" "      " "1  get local a to b"
  created new head
  --------------
  test L:up a   R:nc a b W:       - 1  get local a to b
  --------------
    searching for copies back to rev 1
    unmatched files in other:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: e300d1c794ec+, remote: 4ce40f5aca24
   preserving a for resolve of b
   preserving rev for resolve of rev
   a: remote unchanged -> k
   b: remote copied from a -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging a and b to b
  my b@e300d1c794ec+ other b@4ce40f5aca24 ancestor a@924404dff337
   premerge successful
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@e300d1c794ec+ other rev@4ce40f5aca24 ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
    a
  C a
  --------------
  
  $ tm "nc a b" "up a  " "      " "2  get rem change to a and b"
  created new head
  --------------
  test L:nc a b R:up a   W:       - 2  get rem change to a and b
  --------------
    searching for copies back to rev 1
    unmatched files in local:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 86a2aa42fc76+, remote: f4db7e329e71
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: remote is newer -> g
  getting a
  updating: a 1/3 files (33.33%)
   b: local copied/moved from a -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b and a to b
  my b@86a2aa42fc76+ other a@f4db7e329e71 ancestor a@924404dff337
   premerge successful
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@86a2aa42fc76+ other rev@f4db7e329e71 ancestor rev@924404dff337
  1 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M a
  M b
    a
  --------------
  
  $ tm "up a  " "nm a b" "      " "3  get local a change to b, remove a"
  created new head
  --------------
  test L:up a   R:nm a b W:       - 3  get local a change to b, remove a
  --------------
    searching for copies back to rev 1
    unmatched files in other:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: e300d1c794ec+, remote: bdb19105162a
   preserving a for resolve of b
   preserving rev for resolve of rev
  removing a
   b: remote moved from a -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging a and b to b
  my b@e300d1c794ec+ other b@bdb19105162a ancestor a@924404dff337
   premerge successful
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@e300d1c794ec+ other rev@bdb19105162a ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
    a
  --------------
  
  $ tm "nm a b" "up a  " "      " "4  get remote change to b"
  created new head
  --------------
  test L:nm a b R:up a   W:       - 4  get remote change to b
  --------------
    searching for copies back to rev 1
    unmatched files in local:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 02963e448370+, remote: f4db7e329e71
   preserving b for resolve of b
   preserving rev for resolve of rev
   b: local copied/moved from a -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b and a to b
  my b@02963e448370+ other a@f4db7e329e71 ancestor a@924404dff337
   premerge successful
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@02963e448370+ other rev@f4db7e329e71 ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
    a
  --------------
  
  $ tm "      " "nc a b" "      " "5  get b"
  created new head
  --------------
  test L:       R:nc a b W:       - 5  get b
  --------------
    searching for copies back to rev 1
    unmatched files in other:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' 
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 94b33a1b7f2d+, remote: 4ce40f5aca24
   preserving rev for resolve of rev
   b: remote created -> g
  getting b
  updating: b 1/2 files (50.00%)
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@94b33a1b7f2d+ other rev@4ce40f5aca24 ancestor rev@924404dff337
  1 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  C a
  --------------
  
  $ tm "nc a b" "      " "      " "6  nothing"
  created new head
  --------------
  test L:nc a b R:       W:       - 6  nothing
  --------------
    searching for copies back to rev 1
    unmatched files in local:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' 
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 86a2aa42fc76+, remote: 97c705ade336
   preserving rev for resolve of rev
   rev: versions differ -> m
  updating: rev 1/1 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@86a2aa42fc76+ other rev@97c705ade336 ancestor rev@924404dff337
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  C a
  C b
  --------------
  
  $ tm "      " "nm a b" "      " "7  get b"
  created new head
  --------------
  test L:       R:nm a b W:       - 7  get b
  --------------
    searching for copies back to rev 1
    unmatched files in other:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' 
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 94b33a1b7f2d+, remote: bdb19105162a
   preserving rev for resolve of rev
   a: other deleted -> r
  removing a
  updating: a 1/3 files (33.33%)
   b: remote created -> g
  getting b
  updating: b 2/3 files (66.67%)
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@94b33a1b7f2d+ other rev@bdb19105162a ancestor rev@924404dff337
  1 files updated, 1 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  --------------
  
  $ tm "nm a b" "      " "      " "8  nothing"
  created new head
  --------------
  test L:nm a b R:       W:       - 8  nothing
  --------------
    searching for copies back to rev 1
    unmatched files in local:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' 
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 02963e448370+, remote: 97c705ade336
   preserving rev for resolve of rev
   rev: versions differ -> m
  updating: rev 1/1 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@02963e448370+ other rev@97c705ade336 ancestor rev@924404dff337
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  C b
  --------------
  
  $ tm "um a b" "um a b" "      " "9  do merge with ancestor in a"
  created new head
  --------------
  test L:um a b R:um a b W:       - 9  do merge with ancestor in a
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 62e7bf090eba+, remote: 49b6d8032493
   preserving b for resolve of b
   preserving rev for resolve of rev
   b: both renamed from a -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@62e7bf090eba+ other b@49b6d8032493 ancestor a@924404dff337
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@62e7bf090eba+ other rev@49b6d8032493 ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  --------------
  

m "um a c" "um x c" "      " "10 do merge with no ancestor"

  $ tm "nm a b" "nm a c" "      " "11 get c, keep b"
  created new head
  --------------
  test L:nm a b R:nm a c W:       - 11 get c, keep b
  --------------
    searching for copies back to rev 1
    unmatched files in local:
     b
    unmatched files in other:
     c
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' !
     src: 'a' -> dst: 'c' !
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 02963e448370+, remote: fe905ef2c33e
   preserving rev for resolve of rev
   c: remote created -> g
  getting c
  updating: c 1/2 files (50.00%)
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@02963e448370+ other rev@fe905ef2c33e ancestor rev@924404dff337
  note: possible conflict - a was renamed multiple times to:
   b
   c
  1 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M c
  C b
  --------------
  
  $ tm "nc a b" "up b  " "      " "12 merge b no ancestor"
  created new head
  --------------
  test L:nc a b R:up b   W:       - 12 merge b no ancestor
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 86a2aa42fc76+, remote: af30c7647fc7
   preserving b for resolve of b
   preserving rev for resolve of rev
   b: both created -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@86a2aa42fc76+ other b@af30c7647fc7 ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@86a2aa42fc76+ other rev@af30c7647fc7 ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  C a
  --------------
  
  $ tm "up b  " "nm a b" "      " "13 merge b no ancestor"
  created new head
  --------------
  test L:up b   R:nm a b W:       - 13 merge b no ancestor
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 59318016310c+, remote: bdb19105162a
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: other deleted -> r
  removing a
  updating: a 1/3 files (33.33%)
   b: both created -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@59318016310c+ other b@bdb19105162a ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@59318016310c+ other rev@bdb19105162a ancestor rev@924404dff337
  0 files updated, 2 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  --------------
  
  $ tm "nc a b" "up a b" "      " "14 merge b no ancestor"
  created new head
  --------------
  test L:nc a b R:up a b W:       - 14 merge b no ancestor
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 86a2aa42fc76+, remote: 8dbce441892a
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: remote is newer -> g
  getting a
  updating: a 1/3 files (33.33%)
   b: both created -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@86a2aa42fc76+ other b@8dbce441892a ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@86a2aa42fc76+ other rev@8dbce441892a ancestor rev@924404dff337
  1 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M a
  M b
  --------------
  
  $ tm "up b  " "nm a b" "      " "15 merge b no ancestor, remove a"
  created new head
  --------------
  test L:up b   R:nm a b W:       - 15 merge b no ancestor, remove a
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 59318016310c+, remote: bdb19105162a
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: other deleted -> r
  removing a
  updating: a 1/3 files (33.33%)
   b: both created -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@59318016310c+ other b@bdb19105162a ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@59318016310c+ other rev@bdb19105162a ancestor rev@924404dff337
  0 files updated, 2 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  --------------
  
  $ tm "nc a b" "up a b" "      " "16 get a, merge b no ancestor"
  created new head
  --------------
  test L:nc a b R:up a b W:       - 16 get a, merge b no ancestor
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 86a2aa42fc76+, remote: 8dbce441892a
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: remote is newer -> g
  getting a
  updating: a 1/3 files (33.33%)
   b: both created -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@86a2aa42fc76+ other b@8dbce441892a ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@86a2aa42fc76+ other rev@8dbce441892a ancestor rev@924404dff337
  1 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M a
  M b
  --------------
  
  $ tm "up a b" "nc a b" "      " "17 keep a, merge b no ancestor"
  created new head
  --------------
  test L:up a b R:nc a b W:       - 17 keep a, merge b no ancestor
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 0b76e65c8289+, remote: 4ce40f5aca24
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: remote unchanged -> k
   b: both created -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@0b76e65c8289+ other b@4ce40f5aca24 ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@0b76e65c8289+ other rev@4ce40f5aca24 ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  C a
  --------------
  
  $ tm "nm a b" "up a b" "      " "18 merge b no ancestor"
  created new head
  --------------
  test L:nm a b R:up a b W:       - 18 merge b no ancestor
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 02963e448370+, remote: 8dbce441892a
  remote changed a which local deleted
  use (c)hanged version or leave (d)eleted? c
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: prompt recreating -> g
  getting a
  updating: a 1/3 files (33.33%)
   b: both created -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@02963e448370+ other b@8dbce441892a ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@02963e448370+ other rev@8dbce441892a ancestor rev@924404dff337
  1 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M a
  M b
  --------------
  
  $ tm "up a b" "nm a b" "      " "19 merge b no ancestor, prompt remove a"
  created new head
  --------------
  test L:up a b R:nm a b W:       - 19 merge b no ancestor, prompt remove a
  --------------
    searching for copies back to rev 1
    unmatched files new in both:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 0b76e65c8289+, remote: bdb19105162a
  local changed a which remote deleted
  use (c)hanged version or (d)elete? c
   preserving b for resolve of b
   preserving rev for resolve of rev
   a: prompt keep -> a
  updating: a 1/3 files (33.33%)
   b: both created -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b
  my b@0b76e65c8289+ other b@bdb19105162a ancestor b@000000000000
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@0b76e65c8289+ other rev@bdb19105162a ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
  C a
  --------------
  
  $ tm "up a  " "um a b" "      " "20 merge a and b to b, remove a"
  created new head
  --------------
  test L:up a   R:um a b W:       - 20 merge a and b to b, remove a
  --------------
    searching for copies back to rev 1
    unmatched files in other:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: e300d1c794ec+, remote: 49b6d8032493
   preserving a for resolve of b
   preserving rev for resolve of rev
  removing a
   b: remote moved from a -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging a and b to b
  my b@e300d1c794ec+ other b@49b6d8032493 ancestor a@924404dff337
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@e300d1c794ec+ other rev@49b6d8032493 ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
    a
  --------------
  
  $ tm "um a b" "up a  " "      " "21 merge a and b to b"
  created new head
  --------------
  test L:um a b R:up a   W:       - 21 merge a and b to b
  --------------
    searching for copies back to rev 1
    unmatched files in local:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 62e7bf090eba+, remote: f4db7e329e71
   preserving b for resolve of b
   preserving rev for resolve of rev
   b: local copied/moved from a -> m
  updating: b 1/2 files (50.00%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b and a to b
  my b@62e7bf090eba+ other a@f4db7e329e71 ancestor a@924404dff337
   rev: versions differ -> m
  updating: rev 2/2 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@62e7bf090eba+ other rev@f4db7e329e71 ancestor rev@924404dff337
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
    a
  --------------
  

m "nm a b" "um x a" "      " "22 get a, keep b"

  $ tm "nm a b" "up a c" "      " "23 get c, keep b"
  created new head
  --------------
  test L:nm a b R:up a c W:       - 23 get c, keep b
  --------------
    searching for copies back to rev 1
    unmatched files in local:
     b
    unmatched files in other:
     c
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 924404dff337, local: 02963e448370+, remote: 2b958612230f
   preserving b for resolve of b
   preserving rev for resolve of rev
   c: remote created -> g
  getting c
  updating: c 1/3 files (33.33%)
   b: local copied/moved from a -> m
  updating: b 2/3 files (66.67%)
  picked tool 'python ../merge' for b (binary False symlink False)
  merging b and a to b
  my b@02963e448370+ other a@2b958612230f ancestor a@924404dff337
   premerge successful
   rev: versions differ -> m
  updating: rev 3/3 files (100.00%)
  picked tool 'python ../merge' for rev (binary False symlink False)
  merging rev
  my rev@02963e448370+ other rev@2b958612230f ancestor rev@924404dff337
  1 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  --------------
  M b
    a
  M c
  --------------
  

  $ cd ..


Systematic and terse testing of merge merges and ancestor calculation:

Expected result:

\  a  m1  m2  dst
0  -   f   f   f   "versions differ"
1  f   g   g   g   "versions differ"
2  f   f   f   f   "versions differ"
3  f   f   g  f+g  "remote copied to " + f
4  f   f   g   g   "remote moved to " + f
5  f   g   f  f+g  "local copied to " + f2
6  f   g   f   g   "local moved to " + f2
7  -  (f)  f   f   "remote differs from untracked local"
8  f  (f)  f   f   "remote differs from untracked local"

  $ hg init ancestortest
  $ cd ancestortest
  $ for x in 1 2 3 4 5 6 8; do mkdir $x; echo a > $x/f; done
  $ hg ci -Aqm "a"
  $ mkdir 0
  $ touch 0/f
  $ hg mv 1/f 1/g
  $ hg cp 5/f 5/g
  $ hg mv 6/f 6/g
  $ hg rm 8/f
  $ for x in */*; do echo m1 > $x; done
  $ hg ci -Aqm "m1"
  $ hg up -qr0
  $ mkdir 0 7
  $ touch 0/f 7/f
  $ hg mv 1/f 1/g
  $ hg cp 3/f 3/g
  $ hg mv 4/f 4/g
  $ for x in */*; do echo m2 > $x; done
  $ hg ci -Aqm "m2"
  $ hg up -qr1
  $ mkdir 7 8
  $ echo m > 7/f
  $ echo m > 8/f
  $ hg merge -f --tool internal:dump -v --debug -r2 | sed '/^updating:/,$d' 2> /dev/null
    searching for copies back to rev 1
    unmatched files in local:
     5/g
     6/g
    unmatched files in other:
     3/g
     4/g
     7/f
    unmatched files new in both:
     0/f
     1/g
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: '3/f' -> dst: '3/g' *
     src: '4/f' -> dst: '4/g' *
     src: '5/f' -> dst: '5/g' *
     src: '6/f' -> dst: '6/g' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: True, partial: False
   ancestor: e6cb3cf11019, local: ec44bf929ab5+, remote: c62e34d0b898
  remote changed 8/f which local deleted
  use (c)hanged version or leave (d)eleted? c
   preserving 0/f for resolve of 0/f
   preserving 1/g for resolve of 1/g
   preserving 2/f for resolve of 2/f
   preserving 3/f for resolve of 3/f
   preserving 3/f for resolve of 3/g
   preserving 4/f for resolve of 4/g
   preserving 5/f for resolve of 5/f
   preserving 5/g for resolve of 5/g
   preserving 6/g for resolve of 6/g
   preserving 7/f for resolve of 7/f
  removing 4/f
   8/f: prompt recreating -> g
  getting 8/f
  $ hg mani
  0/f
  1/g
  2/f
  3/f
  4/f
  5/f
  5/g
  6/g
  $ for f in */*; do echo $f:; cat $f; done
  0/f:
  m1
  0/f.base:
  0/f.local:
  m1
  0/f.orig:
  m1
  0/f.other:
  m2
  1/g:
  m1
  1/g.base:
  a
  1/g.local:
  m1
  1/g.orig:
  m1
  1/g.other:
  m2
  2/f:
  m1
  2/f.base:
  a
  2/f.local:
  m1
  2/f.orig:
  m1
  2/f.other:
  m2
  3/f:
  m1
  3/f.base:
  a
  3/f.local:
  m1
  3/f.orig:
  m1
  3/f.other:
  m2
  3/g:
  m1
  3/g.base:
  a
  3/g.local:
  m1
  3/g.orig:
  m1
  3/g.other:
  m2
  4/g:
  m1
  4/g.base:
  a
  4/g.local:
  m1
  4/g.orig:
  m1
  4/g.other:
  m2
  5/f:
  m1
  5/f.base:
  a
  5/f.local:
  m1
  5/f.orig:
  m1
  5/f.other:
  m2
  5/g:
  m1
  5/g.base:
  a
  5/g.local:
  m1
  5/g.orig:
  m1
  5/g.other:
  m2
  6/g:
  m1
  6/g.base:
  a
  6/g.local:
  m1
  6/g.orig:
  m1
  6/g.other:
  m2
  7/f:
  m
  7/f.base:
  7/f.local:
  m
  7/f.orig:
  m
  7/f.other:
  m2
  8/f:
  m2
  $ cd ..