==============

Topic Tutorial

==============

.. This test file is also supposed to be able to compile as a rest file.

.. Some Setup::

  $ . "$TESTDIR/testlib/topic_setup.sh"

  $ hg init server

  $ cd server

  $ cat >> .hg/hgrc << EOF

  > [ui]

  > user= Shopping Master

  > EOF

  $ cat >> shopping << EOF

  > Spam

  > Whizzo butter

  > Albatross

  > Rat (rather a lot)

  > Jugged fish

  > Blancmange

  > Salmon mousse

  > EOF

  $ hg commit -A -m "Shopping list"

  adding shopping

  $ cd ..

  $ hg clone server client

  updating to branch default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd client

  $ cat >> .hg/hgrc << EOF

  > [ui]

  > user= Tutorial User

  > EOF

Topic branches are lightweight branches which disappear when changes are

finalized (move to the public phase). They can help users to organise and share

their unfinished work.

Topic Basics

============

Let's says we use Mercurial to manage our shopping list::

  $ hg log --graph

  @  changeset:   0:38da43f0a2ea

     tag:         tip

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     Shopping list

We are about to do some edition to this list and would like to do them within

a topic. Creating a new topic is done using the ``topic`` command::

  $ hg topic food

As for named branch, our topic is active but it does not contains any changesets yet::

  $ hg topic

   * food

  $ hg summary

  parent: 0:38da43f0a2ea tip

   Shopping list

  branch: default

  commit: (clean)

  update: (current)

  topic:  food

  $ hg log --graph

  @  changeset:   0:38da43f0a2ea

     tag:         tip

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     Shopping list

Our next commit will be part of the active topic::

  $ cat >> shopping << EOF

  > Egg

  > Suggar

  > Vinegar

  > Oil

  > EOF

  $ hg commit -m "adding condiments"

  $ hg log --graph --rev 'topic("food")'

  @  changeset:   1:13900241408b

  |  tag:         tip

  ~  topic:       food

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     adding condiments

And future commit will be part of that topic too::

  $ cat >> shopping << EOF

  > Bananas

  > Pear

  > Apple

  > EOF

  $ hg commit -m "adding fruits"

  $ hg log --graph --rev 'topic("food")'

  @  changeset:   2:287de11b401f

  |  tag:         tip

  |  topic:       food

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     adding fruits

  |

  o  changeset:   1:13900241408b

  |  topic:       food

  ~  user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     adding condiments

We can get a compact view of the content of our topic using the ``stack`` command::

  $ hg stack

  ### topic: food

  ### branch: default

  t2@ adding fruits (current)

  t1: adding condiments

    ^ Shopping list

The topic desactivate when we update away from it::

  $ hg up default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg topic

     food

Note that ``default`` (name of the branch) now refers to the tipmost changeset of default without a topic::

  $ hg log --graph

  o  changeset:   2:287de11b401f

  |  tag:         tip

  |  topic:       food

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     adding fruits

  |

  o  changeset:   1:13900241408b

  |  topic:       food

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     adding condiments

  |

  @  changeset:   0:38da43f0a2ea

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     Shopping list

And updating back to the topic reactivate it::

  $ hg up food

  switching to topic food

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg topic

   * food

The name used for updating does not affect the activation of the topic, updating to a revision part of a topic will activate it in all cases::

  $ hg up default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg up --rev 'desc("condiments")'

  switching to topic food

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg topic

   * food

.. server side activity::

  $ cd ../server/

  $ cat > shopping << EOF

  > T-Shirt

  > Trousers

  > Spam

  > Whizzo butter

  > Albatross

  > Rat (rather a lot)

  > Jugged fish

  > Blancmange

  > Salmon mousse

  > EOF

  $ hg commit -A -m "Adding clothes"

  $ cd ../client

Topic will also affect rebase and merge destination. Let's pull the latest update from the main server::

  $ hg pull

  searching for changes

  adding changesets

  adding manifests

  adding file changes

  added 1 changesets with 1 changes to 1 files (+1 heads)

  (run 'hg heads' to see heads)

  $ hg log -G

  o  changeset:   3:6104862e8b84

  |  tag:         tip

  |  parent:      0:38da43f0a2ea

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     Adding clothes

  |

  | o  changeset:   2:287de11b401f

  | |  topic:       food

  | |  user:        test

  | |  date:        Thu Jan 01 00:00:00 1970 +0000

  | |  summary:     adding fruits

  | |

  | @  changeset:   1:13900241408b

  |/   topic:       food

  |    user:        test

  |    date:        Thu Jan 01 00:00:00 1970 +0000

  |    summary:     adding condiments

  |

  o  changeset:   0:38da43f0a2ea

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     Shopping list

The topic head will not be considered when merge from the new head of the branch::

  $ hg up default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg merge

  abort: branch 'default' has one head - please merge with an explicit rev

  (run 'hg heads' to see all heads)

  [255]

But the topic will see that branch head as a valid destination::

  $ hg up food

  switching to topic food

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg rebase

  rebasing 1:13900241408b "adding condiments"

  merging shopping

  rebasing 2:287de11b401f "adding fruits"

  merging shopping

  $ hg log --graph

  @  changeset:   5:2d50db8b5b4c

  |  tag:         tip

  |  topic:       food

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     adding fruits

  |

  o  changeset:   4:4011b46eeb33

  |  topic:       food

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     adding condiments

  |

  o  changeset:   3:6104862e8b84

  |  parent:      0:38da43f0a2ea

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     Adding clothes

  |

  o  changeset:   0:38da43f0a2ea

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     Shopping list

The topic information will fade out when we publish the changesets::

  $ hg topic

     food

  $ hg push

  searching for changes

  adding changesets

  adding manifests

  adding file changes

  added 2 changesets with 2 changes to 1 files

  2 new obsolescence markers

  $ hg topic

  $ hg log --graph

  @  changeset:   5:2d50db8b5b4c

  |  tag:         tip

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     adding fruits

  |

  o  changeset:   4:4011b46eeb33

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     adding condiments

  |

  o  changeset:   3:6104862e8b84

  |  parent:      0:38da43f0a2ea

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     Adding clothes

  |

  o  changeset:   0:38da43f0a2ea

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     Shopping list

  $ hg up default

  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

Working with Multiple Topics

============================

In the above example, topic are not bring much benefit since you only have one

line of developement. Topic start to be more useful when you have to work on

multiple features are the same time.

We might go shopping in a hardware store in the same go, so let's add some

tools to the shopping list withing a new topic::

  $ hg topic tools

  $ echo hammer >> shopping

  $ hg ci -m 'Adding hammer'

  $ echo saw >> shopping

  $ hg ci -m 'Adding saw'

  $ echo drill >> shopping

  $ hg ci -m 'Adding drill'

But are not sure to actually go in the hardward store, so in the meantime, we

want to extend the list with drinks. We go back to the official default branch

and start a new topic::

  $ hg up default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg topic drinks

  $ echo 'apple juice' >> shopping

  $ hg ci -m 'Adding apple juice'

  $ echo 'orange juice' >> shopping

  $ hg ci -m 'Adding orange juice'

We now have two topics::

  $ hg topic

   * drinks

     tools

The information ``hg stack`` command adapt to the active topic::

  $ hg stack

  ### topic: drinks

  ### branch: default

  t2@ Adding orange juice (current)

  t1: Adding apple juice

    ^ adding fruits

  $ hg up tools

  switching to topic tools

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg stack

  ### topic: tools

  ### branch: default

  t3@ Adding drill (current)

  t2: Adding saw

  t1: Adding hammer

    ^ adding fruits

They are seen as independant branch by Mercurial. No rebase or merge betwen them will be attempted by default::

  $ hg rebase

  nothing to rebase

  [1]

.. server activity::

  $ cd ../server

  $ hg up

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ mv shopping foo

  $ echo 'Coat' > shopping

  $ cat foo >> shopping

  $ hg ci -m 'add a coat'

  $ echo 'Coat' > shopping

  $ echo 'Shoes' >> shopping

  $ cat foo >> shopping

  $ hg rm foo

  not removing foo: file is untracked

  [1]

  $ hg ci -m 'add a pair of shoes'

  $ cd ../client

Lets see what other people did in the mean time::

  $ hg pull

  searching for changes

  adding changesets

  adding manifests

  adding file changes

  added 2 changesets with 2 changes to 1 files (+1 heads)

  (run 'hg heads' to see heads)

There is new changes! We can simply use ``hg rebase`` to update our changeset on top of the latest::

  $ hg rebase

  rebasing 6:183984ef46d1 "Adding hammer"

  merging shopping

  rebasing 7:cffff85af537 "Adding saw"

  merging shopping

  rebasing 8:34255b455dac "Adding drill"

  merging shopping

But what about the other topic? You can use 'hg topic --verbose' to see information about them::

  $ hg topic --verbose

     drinks (on branch: default, 2 changesets, 2 behind)

     tools  (on branch: default, 3 changesets)

The "2 behind" is telling you that there is 2 new changesets on the named branch of the topic. You need to merge or rebase to incorporate them.

Pushing that topic would create a new heads will be prevented::

  $ hg push --rev drinks

  searching for changes

  abort: push creates new remote head 70dfa201ed73!

  (merge or see 'hg help push' for details about pushing new heads)

  [255]

Even after a rebase Pushing all active topics at the same time will complains about the multiple heads it would create on that branch::

  $ hg rebase -b drinks

  rebasing 9:8dfa45bd5e0c "Adding apple juice"

  merging shopping

  rebasing 10:70dfa201ed73 "Adding orange juice"

  merging shopping

  switching to topic tools

  $ hg push

  searching for changes

  abort: push creates new remote head 4cd7c1591a67!

  (merge or see 'hg help push' for details about pushing new heads)

  [255]

Publishing only one of them is allowed (as long as it does not create a new branch head has we just saw in the previous case)::