view tests/test-tutorial.t @ 996:b98dd5d3065c

fold: overhaul handling of revisions with --rev (BC)

The fold command parsed the revision arguments in a very peculiar and
idiosyncratic fashion: if revisions were passed without a --rev
argument, then they would all be extended to ".", but if they were
passed with --rev, then no extension would happen. Passing revisions
both with and without --rev would abort. This is inconsistent with the
way all other hg commands parse revision arguments. We have several
examples of command where several revisions are passed, and the --rev
option is optional for specifying those revisions (update, strip,
export).

This patch alters the way in which fold parses its revision arguments.
No distinction is made between revisions passed with or without the
--rev argument. Regardless if a single or multiple revision is
specified, all will be folded together into the parent of the working
directory. If the --exact argument is passed, then the parent of the
working directory is ignored and the specified revisions must be a
single contiguous line.

The docstring and tests are modified accordingly.

Initial setup
-------------

This Mercurial configuration example is used for testing.
.. Various setup

  $ cat >> $HGRCPATH << EOF
  > [ui]
  > # This is change the default output of log for clear tutorial
  > logtemplate ="{node|short} ({phase}): {desc}\n"
  > [diff]
  > # use "git" diff format, clearer and smarter format
  > git = 1
  > [alias]
  > # "-d '0 0'" means that the new commit will be at January 1st 1970.
  > # This is used for stable hash during test
  > # (this tutorial is automatically tested.)
  > amend = amend -d '0 0'
  > EOF

  $ hg init local
  $ cat >> local/.hg/hgrc << EOF
  > [paths]
  > remote = ../remote
  > other = ../other
  > [ui]
  > user = Babar the King
  > EOF

  $ hg init remote
  $ cat >> remote/.hg/hgrc << EOF
  > [paths]
  > local = ../local
  > [ui]
  > user = Celestine the Queen
  > EOF

  $ hg init other
  $ cat >> other/.hg/hgrc << EOF
  > [ui]
  > user = Princess Flore
  > EOF


This tutorial uses the following configuration for Mercurial:

A compact log template with phase data:

  $ hg showconfig ui | grep log
  ui.logtemplate="{node|short} ({phase}): {desc}\n"

Improved git format diff:

  $ hg showconfig diff
  diff.git=1

And of course, we enable the experimental extensions for mutable history:

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > evolve = $TESTDIR/../hgext/evolve.py
  > # enabling rebase is also needed for now
  > rebase =
  > EOF

-----------------------
Single Developer Usage
-----------------------

This tutorial shows how to use evolution to rewrite history locally.


Fixing mistake with `hg amend`
--------------------------------

We are versionning a shopping list

  $ cd local
  $ cat  >> shopping << EOF
  > Spam
  > Whizzo butter
  > Albatross
  > Rat (rather a lot)
  > Jugged fish
  > Blancmange
  > Salmon mousse
  > EOF
  $ hg commit -A -m "Monthy Python Shopping list"
  adding shopping

Its first version is shared with the outside.

  $ hg push remote
  pushing to $TESTTMP/remote
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

Later I add additional item to my list

  $ cat >> shopping << EOF
  > Egg
  > Suggar
  > Vinegar
  > Oil
  > EOF
  $ hg commit -m "adding condiment"
  $ cat >> shopping << EOF
  > Bananos
  > Pear
  > Apple
  > EOF
  $ hg commit -m "adding fruit"

This history is very linear

  $ hg log -G
  @  d85de4546133 (draft): adding fruit
  |
  o  4d5dc8187023 (draft): adding condiment
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

But a typo was made in Babanas!

  $ hg export tip
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID d85de4546133030c82d257bbcdd9b1b416d0c31c
  # Parent  4d5dc81870237d492284826e21840b2ca00e26d1
  adding fruit
  
  diff --git a/shopping b/shopping
  --- a/shopping
  +++ b/shopping
  @@ -9,3 +9,6 @@
   Suggar
   Vinegar
   Oil
  +Bananos
  +Pear
  +Apple

The faulty changeset is in the "draft" phase because it has not been exchanged with
the outside. The first one has been exchanged and is "public" (immutable).

  $ hg log -G
  @  d85de4546133 (draft): adding fruit
  |
  o  4d5dc8187023 (draft): adding condiment
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

hopefully. I can use `hg commit --amend` to rewrite my faulty changeset!

  $ sed -i'' -e s/Bananos/Banana/ shopping
  $ hg diff
  diff --git a/shopping b/shopping
  --- a/shopping
  +++ b/shopping
  @@ -9,6 +9,6 @@
   Suggar
   Vinegar
   Oil
  -Bananos
  +Banana
   Pear
   Apple
  $ hg commit --amend

A new changeset with the right diff replace the wrong one.

  $ hg log -G
  @  9d0363b81950 (draft): adding fruit
  |
  o  4d5dc8187023 (draft): adding condiment
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  
  $ hg export tip
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID 9d0363b81950646bc6ad1ec5de8b8197ea586541
  # Parent  4d5dc81870237d492284826e21840b2ca00e26d1
  adding fruit
  
  diff --git a/shopping b/shopping
  --- a/shopping
  +++ b/shopping
  @@ -9,3 +9,6 @@
   Suggar
   Vinegar
   Oil
  +Banana
  +Pear
  +Apple

Getting rid of branchy history
----------------------------------

While I was working on my list. someone made a change remotly.

  $ cd ../remote
  $ hg up -q
  $ sed -i'' -e 's/Spam/Spam Spam Spam/' shopping
  $ hg ci -m 'SPAM'
  $ cd ../local

I'll get this remote changeset when pulling

  $ hg pull remote
  pulling from $TESTTMP/remote
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  OBSEXC: pull obsolescence markers
  OBSEXC: no unknown remote markers
  OBSEXC: DONE
  (run 'hg heads' to see heads, 'hg merge' to merge)

I now have a new heads. Note that this remote head is immutable

  $ hg log -G
  o  9ca060c80d74 (public): SPAM
  |
  | @  9d0363b81950 (draft): adding fruit
  | |
  | o  4d5dc8187023 (draft): adding condiment
  |/
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

instead of merging my head with the new one. I'm going to rebase my work

  $ hg diff
  $ hg rebase --dest 9ca060c80d74 --source 4d5dc8187023
  merging shopping
  merging shopping


My local work is now rebased on the remote one.

  $ hg log -G
  @  41aff6a42b75 (draft): adding fruit
  |
  o  dfd3a2d7691e (draft): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

Removing changesets
------------------------

I add new item to my list

  $ cat >> shopping << EOF
  > car
  > bus
  > plane
  > boat
  > EOF
  $ hg ci -m 'transport'
  $ hg log -G
  @  1125e39fbf21 (draft): transport
  |
  o  41aff6a42b75 (draft): adding fruit
  |
  o  dfd3a2d7691e (draft): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

I have a new commit but I realize that don't want it. (transport shop list does
not fit well in my standard shopping list)

  $ hg prune . # "." is for working directory parent
  1 changesets pruned
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  working directory now at 41aff6a42b75

The silly changeset is gone.

  $ hg log -G
  @  41aff6a42b75 (draft): adding fruit
  |
  o  dfd3a2d7691e (draft): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

Reordering changesets
------------------------


We create two changesets.


  $ cat >> shopping << EOF
  > Shampoo
  > Toothbrush
  > ... More bathroom stuff to come
  > Towel
  > Soap
  > EOF
  $ hg ci -m 'bathroom stuff' -q # XXX remove the -q

  $ sed -i'' -e 's/Spam/Spam Spam Spam/g' shopping
  $ hg ci -m 'SPAM SPAM'
  $ hg log -G
  @  fac207dec9f5 (draft): SPAM SPAM
  |
  o  10b8aeaa8cc8 (draft): bathroom stuff
  |
  o  41aff6a42b75 (draft): adding fruit
  |
  o  dfd3a2d7691e (draft): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

.. note:: We can't amend changeset 7e82d3f3c2cb or 9ca060c80d74 as they are immutable.

 I now want to push to remote all my changes except the bathroom one, which I'm
 not totally happy with yet. To be able to push "SPAM SPAM" I need a version of
 "SPAM SPAM" which is not a child of "bathroom stuff"

You can use the 'grab' alias for that.

.. note: grab is an alias for `hg rebase --dest . --rev <target>; hg up <there>`

  $ hg up 'p1(10b8aeaa8cc8)' # going on "bathroom stuff" parent
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg grab fac207dec9f5 # moving "SPAM SPAM" to the working directory parent
  merging shopping
  ? files updated, 0 files merged, 0 files removed, 0 files unresolved (glob)
  $ hg log -G
  @  a224f2a4fb9f (draft): SPAM SPAM
  |
  | o  10b8aeaa8cc8 (draft): bathroom stuff
  |/
  o  41aff6a42b75 (draft): adding fruit
  |
  o  dfd3a2d7691e (draft): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

We have a new SPAM SPAM version without the bathroom stuff

  $ grep Spam shopping  # enough spam
  Spam Spam Spam Spam Spam Spam Spam Spam Spam
  $ grep Toothbrush shopping # no Toothbrush
  [1]
  $ hg export .
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID a224f2a4fb9f9f828f608959912229d7b38b26de
  # Parent  41aff6a42b7578ec7ec3cb2041633f1ca43cca96
  SPAM SPAM
  
  diff --git a/shopping b/shopping
  --- a/shopping
  +++ b/shopping
  @@ -1,4 +1,4 @@
  -Spam Spam Spam
  +Spam Spam Spam Spam Spam Spam Spam Spam Spam
   Whizzo butter
   Albatross
   Rat (rather a lot)

To make sure I do not push unready changeset by mistake I set the "bathroom
stuff" changeset in the secret phase.

  $ hg phase --force --secret 10b8aeaa8cc8

we can now push our change:

  $ hg push remote
  pushing to $TESTTMP/remote
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files
  OBSEXC: computing relevant nodes
  OBSEXC: computing markers relevant to 5 nodes
  OBSEXC: pushing 6 markers (487 bytes)
  OBSEXC: DONE

for simplicity sake we get the bathroom change in line again

  $ hg grab 10b8aeaa8cc8
  merging shopping
  ? files updated, 0 files merged, 0 files removed, 0 files unresolved (glob)
  $ hg phase --draft .
  $ hg log -G
  @  75954b8cd933 (draft): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  



Splitting change
------------------

This part is not written yet, but you can use either the `histedit` extension
of the `uncommit` command to splitting a change.

  $ hg help uncommit
  hg uncommit [OPTION]... [NAME]
  
  move changes from parent revision to working directory
  
      Changes to selected files in the checked out revision appear again as
      uncommitted changed in the working directory. A new revision without the
      selected changes is created, becomes the checked out revision, and
      obsoletes the previous one.
  
      The --include option specifies patterns to uncommit. The --exclude option
      specifies patterns to keep in the commit.
  
      Return 0 if changed files are uncommitted.
  
  options:
  
   -a --all                 uncommit all changes when no arguments given
   -I --include PATTERN [+] include names matching the given patterns
   -X --exclude PATTERN [+] exclude names matching the given patterns
  
  [+] marked option can be specified multiple times
  
  use "hg -v help uncommit" to show the global options


The edit command of histedit can be used to split changeset:


Collapsing change
------------------

The tutorial part is not written yet but can use `hg fold`:

  $ hg help fold
  hg fold [OPTION]... [-r] REV
  
  aliases: squash
  
  fold multiple revisions into a single one
  
      Folds a set of revisions with the parent of the working directory. All
      revisions linearly between the given revisions and the parent of the
      working directory will also be folded.
  
      Use --exact for folding only the specified revisions while ignoring the
      parent of the working directory. In this case, the given revisions must
      form a linear unbroken chain.
  
  options:
  
   -r --rev VALUE [+] revision to fold
      --exact         only fold specified revisions
   -m --message TEXT  use text as commit message
   -l --logfile FILE  read commit message from file
   -d --date DATE     record the specified date as commit date
   -u --user USER     record the specified user as committer
  
  [+] marked option can be specified multiple times
  
  use "hg -v help fold" to show more complete help and the global options


-----------------------
Collaboration
-----------------------


sharing mutable changesets
----------------------------

To share mutable changesets with others, just check that the repo you interact
with is "not publishing". Otherwise you will get the previously observe
behavior where exchanged changeset are automatically published.

  $ cd ../remote
  $ hg -R ../local/ showconfig phases

the localrepo does not have any specific configuration for `phases.publish`. It
is ``true`` by default.

  $ hg pull local
  pulling from $TESTTMP/local
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  OBSEXC: pull obsolescence markers
  OBSEXC: merging obsolescence markers (560 bytes)
  OBSEXC: 1 markers added
  OBSEXC: DONE
  (run 'hg update' to get a working copy)
  $ hg log -G
  o  75954b8cd933 (public): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  @  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  



We do not want to publish the "bathroom changeset". Let's rollback the last transaction.

.. Warning: Rollback is actually a dangerous kind of internal command that is deprecated and should not be exposed to user. Please forget you read about it until someone fix this tutorial.

  $ hg rollback
  repository tip rolled back to revision 4 (undo pull)
  $ hg log -G
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  @  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

Let's make the local repo "non publishing"

  $ echo '[phases]' >> ../local/.hg/hgrc
  $ echo 'publish=false' >> ../local/.hg/hgrc
  $ echo '[phases]' >> .hg/hgrc
  $ echo 'publish=false' >> .hg/hgrc
  $ hg showconfig phases
  phases.publish=false
  $ hg -R ../local/ showconfig phases
  phases.publish=false


I can now exchange mutable changeset between "remote" and "local" repository.

  $ hg pull local
  pulling from $TESTTMP/local
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  OBSEXC: pull obsolescence markers
  OBSEXC: merging obsolescence markers (560 bytes)
  OBSEXC: 1 markers added
  OBSEXC: DONE
  (run 'hg update' to get a working copy)
  $ hg log -G
  o  75954b8cd933 (draft): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  @  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

Rebasing unstable change after pull
----------------------------------------------

Remotely someone add a new changeset on top of the mutable "bathroom" on.

  $ hg up 75954b8cd933 -q
  $ cat >> shopping << EOF
  > Giraffe
  > Rhino
  > Lion
  > Bear
  > EOF
  $ hg ci -m 'animals'

But at the same time, locally, this same "bathroom changeset" was updated.

  $ cd ../local
  $ hg up 75954b8cd933 -q
  $ sed -i'' -e 's/... More bathroom stuff to come/Bath Robe/' shopping
  $ hg commit --amend
  $ hg log -G
  @  a44c85f957d3 (draft): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  


When we pull from remote again we get an unstable state!

  $ hg pull remote
  pulling from $TESTTMP/remote
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  OBSEXC: pull obsolescence markers
  OBSEXC: merging obsolescence markers (560 bytes)
  OBSEXC: 0 markers added
  OBSEXC: DONE
  (run 'hg heads' to see heads, 'hg merge' to merge)
  1 new unstable changesets


The new changeset "animal" is based on an old changeset of "bathroom". You can
see both version showing up in the log.

  $ hg log -G
  o  bf1b0d202029 (draft): animals
  |
  | @  a44c85f957d3 (draft): bathroom stuff
  | |
  x |  75954b8cd933 (draft): bathroom stuff
  |/
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

The older version 75954b8cd933 never ceased to exist in the local repo. It was
just hidden and excluded from pull and push.

.. note:: In hgview there is a nice dotted relation highlighting a44c85f957d3 as a new version of 75954b8cd933. this is not yet ported to ``hg log -G``.

There is now an **unstable** changeset in this history. Mercurial will refuse to
share it with the outside:

  $ hg push other
  pushing to $TESTTMP/other
  searching for changes
  abort: push includes unstable changeset: bf1b0d202029!
  (use 'hg evolve' to get a stable history or --force to ignore warnings)
  [255]
 



To resolve this unstable state, you need to rebase bf1b0d202029 onto
a44c85f957d3. The `hg evolve` command will do this for you.

It has a --dry-run option to only suggest the next move.

  $ hg evolve --dry-run
  move:[15] animals
  atop:[14] bathroom stuff
  hg rebase -r bf1b0d202029 -d a44c85f957d3

Let's do it

  $ hg evolve
  move:[15] animals
  atop:[14] bathroom stuff
  merging shopping

The old version of bathroom is hidden again.

  $ hg log -G
  @  ee942144f952 (draft): animals
  |
  o  a44c85f957d3 (draft): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  


We can push this evolution to remote

  $ hg push remote
  pushing to $TESTTMP/remote
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files (+1 heads)
  OBSEXC: computing relevant nodes
  OBSEXC: computing markers relevant to 7 nodes
  OBSEXC: pushing 10 markers (803 bytes)
  OBSEXC: DONE

remote get a warning that current working directory is based on an obsolete changeset

  $ cd ../remote
  $ hg pull local # we up again to trigger the warning. it was displayed during the push
  pulling from $TESTTMP/local
  searching for changes
  no changes found
  OBSEXC: pull obsolescence markers
  OBSEXC: merging obsolescence markers (803 bytes)
  OBSEXC: 0 markers added
  OBSEXC: DONE
  working directory parent is obsolete!

now let's see where we are, and update to the successor

  $ hg parents
  bf1b0d202029 (draft): animals
  working directory parent is obsolete!
  $ hg evolve
  update:[8] animals
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Relocating unstable change after prune
----------------------------------------------

The remote guy keep working

  $ sed -i'' -e 's/Spam/Spam Spam Spam Spam/g' shopping
  $ hg commit -m "SPAM SPAM SPAM"

I'm pulling its work locally.

  $ cd ../local
  $ hg pull remote
  pulling from $TESTTMP/remote
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  OBSEXC: pull obsolescence markers
  OBSEXC: merging obsolescence markers (803 bytes)
  OBSEXC: 0 markers added
  OBSEXC: DONE
  (run 'hg update' to get a working copy)
  $ hg log -G
  o  99f039c5ec9e (draft): SPAM SPAM SPAM
  |
  @  ee942144f952 (draft): animals
  |
  o  a44c85f957d3 (draft): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

In the mean time I noticed you can't buy animals in a super market and I prune the animal changeset:

  $ hg prune ee942144f952
  1 changesets pruned
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  working directory now at a44c85f957d3
  1 new unstable changesets


The animals changeset is still displayed because the "SPAM SPAM SPAM" changeset
is neither dead or obsolete.  My repository is in an unstable state again.

  $ hg log -G
  o  99f039c5ec9e (draft): SPAM SPAM SPAM
  |
  x  ee942144f952 (draft): animals
  |
  @  a44c85f957d3 (draft): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  

  $ hg log -r 'unstable()'
  99f039c5ec9e (draft): SPAM SPAM SPAM

  $ hg evolve
  move:[17] SPAM SPAM SPAM
  atop:[14] bathroom stuff
  merging shopping

  $ hg log -G
  @  40aa40daeefb (draft): SPAM SPAM SPAM
  |
  o  a44c85f957d3 (draft): bathroom stuff
  |
  o  a224f2a4fb9f (public): SPAM SPAM
  |
  o  41aff6a42b75 (public): adding fruit
  |
  o  dfd3a2d7691e (public): adding condiment
  |
  o  9ca060c80d74 (public): SPAM
  |
  o  7e82d3f3c2cb (public): Monthy Python Shopping list
  


Handling Divergent amend
----------------------------------------------

We can detect that multiple diverging amendments have been made.
The `evolve` command can solve this situation. But all corner case are not
handled now.

This section needs to be written.