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

Topic Tutorial

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

This Mercurial configuration example is used for testing.

.. Various 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 organize and share

their unfinished work.

Topic Basics

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

Let's say 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 make some additions 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

Much like a named branch, our topic is active but it does not contain 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 commits 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

  t0^ Shopping list (base)

The topic deactivates when we update away from it:

  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 reactivates it:

  switching to topic food

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

  $ hg topic

   * food

Updating to any changeset that is part of a topic activates the topic

regardless of how the revision was specified:

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

  switching to topic food

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

  $ hg topic

   * food

  $ 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

The topic will also affect the rebase and the merge destinations. Let's pull

the latest update from the main server:

  $ hg pull

  pulling from $TESTTMP/server (glob)

  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 merging from the new head of the

branch:

  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:

  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

  switching to topic food

  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 disappear when we publish the changesets:

  $ hg topic

   * food

  $ hg push

  pushing to $TESTTMP/server (glob)

  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

   * food

  $ 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

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

Working with Multiple Topics

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

In the above example, topics do not bring much benefit since you only have one

line of development. Topics start to be more useful when you have to work on

multiple features at 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 within a new topic:

  $ hg topic tools

  $ echo hammer >> shopping

  $ echo saw >> shopping

  $ echo drill >> shopping

But we are not sure we will actually go to the hardware 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:

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

  $ hg topic drinks

  $ echo 'apple juice' >> shopping

  $ echo 'orange juice' >> shopping

We now have two topics:

  $ hg topic

   * drinks

     tools

The information displayed by ``hg stack`` adapts to the active topic:

  $ hg stack

  ### topic: drinks

  ### branch: default

  t2@ Adding orange juice (current)

  t1: Adding apple juice

  t0^ adding fruits (base)

  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

  t0^ adding fruits (base)

They are seen as independent branches by Mercurial. No rebase or merge

between them will be attempted by default:

  $ hg rebase

  nothing to rebase

  [1]

  $ cd ../server

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

  $ mv shopping foo

  $ echo 'Coat' > shopping

  $ cat foo >> shopping

  $ echo 'Coat' > shopping

  $ echo 'Shoes' >> shopping

  $ cat foo >> shopping

  $ rm foo

  $ cd ../client

Let's see what other people did in the meantime:

  $ hg pull

  pulling from $TESTTMP/server (glob)

  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)