evolve extension for Mercurial

Topic Tutorial

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Topic Tutorial

This Mercurial configuration example is used for testing.

$ . "$TESTDIR/testlib/topic_setup.sh"
$ cat >> $HGRCPATH << EOF
> [experimental]
> evolution=all
> [extensions]
> evolve=
> EOF
$ 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 (moved to the public phase). They can help users to organize and share their unfinished work.

In this tutorial, we explain how to use topics for local development. In the first part, there is a central publishing server. Anything pushed to the central server will become public and immutable. This means no unfinished work should escape the local repository.

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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
}

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 topics food
marked working directory as topic: food

Much like a named branch, our topic is active but it does not contain any changeset yet:

$ hg topics
 * food (0 changesets)
$ 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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
}

Our next commit will be part of the active topic:

$ cat >> shopping << EOF
> Egg
> Suggar
> Vinegar
> Oil
> EOF
$ hg commit -m "adding condiments"
active topic 'food' grew its first changeset
(see 'hg help topics' for more information)
$ 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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  1        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=1,
          pin=true,
          pos="1,1!",
          shape=pentagon,
          style=filled,
          width=1];
}

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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  1        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=1,
          pin=true,
          pos="1,1!",
          shape=pentagon,
          style=filled,
          width=1];
  2        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=2,
          pin=true,
          pos="1,2!",
          shape=pentagon,
          style=filled,
          width=1];
  1 -> 2   [arrowhead=none,
          penwidth=2.0];
}

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

$ hg stack
### topic: food
### target: default (branch)
s2@ adding fruits (current)
s1: adding condiments
s0^ Shopping list (base)

The topic deactivates when we update away from it:

$ hg update default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg topics
   food (2 changesets)

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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
  1        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=1,
          pin=true,
          pos="1,1!",
          shape=pentagon,
          style=filled,
          width=1];
  0 -> 1   [arrowhead=none,
          penwidth=2.0];
  2        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=2,
          pin=true,
          pos="1,2!",
          shape=pentagon,
          style=filled,
          width=1];
  1 -> 2   [arrowhead=none,
          penwidth=2.0];
}

And updating back to the topic reactivates it:

$ hg update food
switching to topic food
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg topics
 * food (2 changesets)

Updating to any changeset that is part of a topic activates the topic regardless of how the revision was specified:

$ hg update default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg update --rev 'desc("condiments")'
switching to topic food
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg topics
 * food (2 changesets)
$ 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)
new changesets 6104862e8b84
(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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
  1        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=1,
          pin=true,
          pos="1,1!",
          shape=pentagon,
          style=filled,
          width=1];
  0 -> 1   [arrowhead=none,
          penwidth=2.0];
  3        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=3,
          pin=true,
          pos="1,3!",
          shape=circle,
          style=filled,
          width=1];
  0 -> 3   [arrowhead=none,
          penwidth=2.0];
  2        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=2,
          pin=true,
          pos="1,2!",
          shape=pentagon,
          style=filled,
          width=1];
  1 -> 2   [arrowhead=none,
          penwidth=2.0];
}

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

$ hg update 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 update food
switching to topic food
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg rebase
rebasing 1:13900241408b "adding condiments" (food)
merging shopping
switching to topic food
rebasing 2:287de11b401f "adding fruits" (food)
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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
  3        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=3,
          pin=true,
          pos="1,3!",
          shape=circle,
          style=filled,
          width=1];
  0 -> 3   [arrowhead=none,
          penwidth=2.0];
  4        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=4,
          pin=true,
          pos="1,4!",
          shape=pentagon,
          style=filled,
          width=1];
  3 -> 4   [arrowhead=none,
          penwidth=2.0];
  5        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=5,
          pin=true,
          pos="1,5!",
          shape=pentagon,
          style=filled,
          width=1];
  4 -> 5   [arrowhead=none,
          penwidth=2.0];
}

There exists a template keyword named “topic” which can be used

$ hg log -GT "{rev}:{node|short} {topic}\n {desc}"
@  5:2d50db8b5b4c food
|   adding fruits
o  4:4011b46eeb33 food
|   adding condiments
o  3:6104862e8b84
|   Adding clothes
o  0:38da43f0a2ea
    Shopping list

The topic information will disappear when we publish the changesets:

$ hg topics
 * food (2 changesets)
$ 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
active topic 'food' is now empty
(use 'hg topic --clear' to clear it if needed)
$ hg topics
 * food (0 changesets)

The topic still exists, and any new commit will be in the topic. But note that it is now devoid of any commit.

$ hg topics --list
### topic: food
### target: default (branch)
(stack is empty)
s0^ adding fruits (base current)
$ 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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
  3        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=3,
          pin=true,
          pos="1,3!",
          shape=circle,
          style=filled,
          width=1];
  0 -> 3   [arrowhead=none,
          penwidth=2.0];
  4        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=4,
          pin=true,
          pos="1,4!",
          shape=circle,
          style=filled,
          width=1];
  3 -> 4   [arrowhead=none,
          penwidth=2.0];
  5        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=5,
          pin=true,
          pos="1,5!",
          shape=circle,
          style=filled,
          width=1];
  4 -> 5   [arrowhead=none,
          penwidth=2.0];
}

If we update to the default head, we will leave the topic behind, and since it is commit-less, it will vanish.

$ hg update default
clearing empty topic "food"
0 files updated, 0 files merged, 0 files removed, 0 files unresolved

From there, the topic has been completely forgotten.

$ hg topics

Keep working within topics

Making sure all your new local commit are made within a topic will help you organize your work. It is possible to ensure this through the Mercurial configuration.

For this tutorial, we’ll add the config at the repository level:

$ cat << EOF >> .hg/hgrc
> [experimental]
> topic-mode = enforce
> EOF

You can also use hg config –edit to update your mercurial configuration.

Once enforcement is turned on. New local commit will be denied if no topic is active.

$ echo sickle >> shopping
$ hg commit -m 'Adding sickle'
abort: no active topic
(see 'hg help -e topic.topic-mode' for details)
[255]

Ok, let’s clean this up and delve into multiple topics.

$ hg revert .
reverting shopping

Working with Multiple Topics

In the above example, topics do not bring many benefits 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 topics tools
marked working directory as topic: tools
$ echo hammer >> shopping
$ hg commit -m 'Adding hammer'
active topic 'tools' grew its first changeset
(see 'hg help topics' for more information)
$ echo saw >> shopping
$ hg commit -m 'Adding saw'
$ echo drill >> shopping
$ hg commit -m 'Adding drill'

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:

$ hg update default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg topics drinks
marked working directory as topic: drinks
$ echo 'apple juice' >> shopping
$ hg commit -m 'Adding apple juice'
active topic 'drinks' grew its first changeset
(see 'hg help topics' for more information)
$ echo 'orange juice' >> shopping
$ hg commit -m 'Adding orange juice'

We now have two topics:

$ hg topics
 * drinks (2 changesets)
   tools  (3 changesets)

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

$ hg stack
### topic: drinks
### target: default (branch)
s2@ Adding orange juice (current)
s1: Adding apple juice
s0^ adding fruits (base)
$ hg update tools
switching to topic tools
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg stack
### topic: tools
### target: default (branch)
s3@ Adding drill (current)
s2: Adding saw
s1: Adding hammer
s0^ 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]

We simulate independant contributions to the repo with this activity:

$ cd ../server
$ hg update
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ mv shopping foo
$ echo 'Coat' > shopping
$ cat foo >> shopping
$ hg commit -m 'add a coat'
$ echo 'Coat' > shopping
$ echo 'Shoes' >> shopping
$ cat foo >> shopping
$ rm foo
$ hg commit -m 'add a pair of shoes'
$ cd ../client

Let’s discover what other people did contribute:

$ 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)
new changesets f2d6cacc6115:fbff9bc37a43
(run 'hg heads' to see heads)

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

$ hg log -G
o  changeset:   12:fbff9bc37a43
|  tag:         tip
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     add a pair of shoes
|
o  changeset:   11:f2d6cacc6115
|  parent:      5:2d50db8b5b4c
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     add a coat
|
| o  changeset:   10:70dfa201ed73
| |  topic:       drinks
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  summary:     Adding orange juice
| |
| o  changeset:   9:8dfa45bd5e0c
|/   topic:       drinks
|    parent:      5:2d50db8b5b4c
|    user:        test
|    date:        Thu Jan 01 00:00:00 1970 +0000
|    summary:     Adding apple juice
|
| @  changeset:   8:34255b455dac
| |  topic:       tools
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  summary:     Adding drill
| |
| o  changeset:   7:cffff85af537
| |  topic:       tools
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  summary:     Adding saw
| |
| o  changeset:   6:183984ef46d1
|/   topic:       tools
|    user:        test
|    date:        Thu Jan 01 00:00:00 1970 +0000
|    summary:     Adding hammer
|
o  changeset:   5:2d50db8b5b4c
|  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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
  3        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=3,
          pin=true,
          pos="1,3!",
          shape=circle,
          style=filled,
          width=1];
  0 -> 3   [arrowhead=none,
          penwidth=2.0];
  4        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=4,
          pin=true,
          pos="1,4!",
          shape=circle,
          style=filled,
          width=1];
  3 -> 4   [arrowhead=none,
          penwidth=2.0];
  5        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=5,
          pin=true,
          pos="1,5!",
          shape=circle,
          style=filled,
          width=1];
  4 -> 5   [arrowhead=none,
          penwidth=2.0];
  6        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=6,
          pin=true,
          pos="1,6!",
          shape=pentagon,
          style=filled,
          width=1];
  5 -> 6   [arrowhead=none,
          penwidth=2.0];
  9        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=9,
          pin=true,
          pos="1,9!",
          shape=pentagon,
          style=filled,
          width=1];
  5 -> 9   [arrowhead=none,
          penwidth=2.0];
  11       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=11,
          pin=true,
          pos="1,11!",
          shape=circle,
          style=filled,
          width=1];
  5 -> 11  [arrowhead=none,
          penwidth=2.0];
  7        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=7,
          pin=true,
          pos="1,7!",
          shape=pentagon,
          style=filled,
          width=1];
  6 -> 7   [arrowhead=none,
          penwidth=2.0];
  8        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=8,
          pin=true,
          pos="1,8!",
          shape=pentagon,
          style=filled,
          width=1];
  7 -> 8   [arrowhead=none,
          penwidth=2.0];
  10       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=10,
          pin=true,
          pos="1,10!",
          shape=pentagon,
          style=filled,
          width=1];
  9 -> 10  [arrowhead=none,
          penwidth=2.0];
  12       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=12,
          pin=true,
          pos="1,12!",
          shape=circle,
          style=filled,
          width=1];
  11 -> 12         [arrowhead=none,
          penwidth=2.0];
}

$ hg rebase
rebasing 6:183984ef46d1 "Adding hammer" (tools)
merging shopping
switching to topic tools
rebasing 7:cffff85af537 "Adding saw" (tools)
merging shopping
rebasing 8:34255b455dac "Adding drill" (tools)
merging shopping

But what about the other topic? You can use ‘hg topics –verbose’ to see information about all the topics:

$ hg topics --verbose
   drinks (on branch: default, 2 changesets, 2 behind)
 * tools  (on branch: default, 3 changesets)

The “2 behind” is telling you that there are 2 new changesets over the base of the topic.

Pushing that topic would create a new head, and therefore will be prevented:

$ hg push --rev drinks
pushing to $TESTTMP/server (glob)
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 would publish them to the default branch, and then mercurial would complain about the multiple public heads it would create on that branch:

$ hg rebase -b drinks
rebasing 9:8dfa45bd5e0c "Adding apple juice" (drinks)
merging shopping
switching to topic drinks
rebasing 10:70dfa201ed73 "Adding orange juice" (drinks)
merging shopping
switching to topic tools
$ hg push
pushing to $TESTTMP/server (glob)
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 as we just saw in the previous case):

$ hg push -r drinks
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

The published topic has now disappeared, and the other is now marked as “behind”:

$ hg topics --verbose
 * tools (on branch: default, 3 changesets, 2 behind)
$ hg stack
### topic: tools
### target: default (branch), 2 behind
s3@ Adding drill (current)
s2: Adding saw
s1: Adding hammer
s0^ add a pair of shoes (base)

Working Within Your Stack

Editing your work mid-stack

It’s easy to edit your work inside your stack:

$ hg stack
### topic: tools
### target: default (branch), 2 behind
s3: Adding drill
s2: Adding saw
s1@ Adding hammer (current)
s0^ add a pair of shoes (base)
$ hg amend -m "Adding hammer to the shopping list"
2 new orphan changesets

Understanding the current situation with hg log is not so easy, because it shows too many things:

$ hg log -G -r "s0::"
@  changeset:   18:b7509bd417f8
|  tag:         tip
|  topic:       tools
|  parent:      12:fbff9bc37a43
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     Adding hammer to the shopping list
|
| o  changeset:   17:4cd7c1591a67
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  summary:     Adding orange juice
| |
| o  changeset:   16:20759cb47ff8
|/   parent:      12:fbff9bc37a43
|    user:        test
|    date:        Thu Jan 01 00:00:00 1970 +0000
|    summary:     Adding apple juice
|
| *  changeset:   15:bb1e6254f532
| |  topic:       tools
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  instability: orphan
| |  summary:     Adding drill
| |
| *  changeset:   14:d4f97f32f8a1
| |  topic:       tools
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  instability: orphan
| |  summary:     Adding saw
| |
| x  changeset:   13:a8ab3599d53d
|/   topic:       tools
|    user:        test
|    date:        Thu Jan 01 00:00:00 1970 +0000
|    obsolete:    reworded using amend as 18:b7509bd417f8
|    summary:     Adding hammer
|
o  changeset:   12:fbff9bc37a43
|  user:        test
~  date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     add a pair of shoes

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  12       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=12,
          pin=true,
          pos="1,12!",
          shape=circle,
          style=filled,
          width=1];
  13       [fillcolor="#DFDFFF",
          fixedsize=true,
          group=default_alt,
          height=1,
          label=13,
          pin=true,
          pos="2,13!",
          shape=pentagon,
          style="dotted, filled",
          width=1];
  12 -> 13         [arrowhead=none,
          penwidth=2.0];
  18       [fillcolor="#7F7FFF",
          fixedsize=true,
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          height=1,
          label=18,
          pin=true,
          pos="1,18!",
          shape=pentagon,
          style=filled,
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  12 -> 18         [arrowhead=none,
          penwidth=2.0];
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          fixedsize=true,
          group=default,
          height=1,
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          pin=true,
          pos="1,16!",
          shape=circle,
          style=filled,
          width=1];
  12 -> 16         [arrowhead=none,
          penwidth=2.0];
  13 -> 18         [arrowtail=none,
          dir=back,
          minlen=0,
          penwidth=2.0,
          style=dashed];
  14       [fillcolor="#FF4F4F",
          fixedsize=true,
          group=default_alt,
          height=1,
          label=14,
          pin=true,
          pos="2,14!",
          shape=pentagon,
          style=filled,
          width=1];
  13 -> 14         [arrowhead=none,
          penwidth=2.0];
  15       [fillcolor="#FF4F4F",
          fixedsize=true,
          group=default_alt,
          height=1,
          label=15,
          pin=true,
          pos="2,15!",
          shape=pentagon,
          style=filled,
          width=1];
  14 -> 15         [arrowhead=none,
          penwidth=2.0];
  17       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=17,
          pin=true,
          pos="1,17!",
          shape=circle,
          style=filled,
          width=1];
  16 -> 17         [arrowhead=none,
          penwidth=2.0];
}

Fortunately stack shows you a better visualization:

$ hg stack
### topic: tools
### target: default (branch), 2 behind
s3$ Adding drill (unstable)
s2$ Adding saw (unstable)
s1@ Adding hammer to the shopping list (current)
s0^ add a pair of shoes (base)

It’s easy to stabilize the situation, next has an –evolve option. It will do the necessary relocation of s2 and s3 over the new s1 without having to do that rebase by hand.:

$ hg next --evolve
move:[14] Adding saw
atop:[18] Adding hammer to the shopping list
working directory now at d5c51ee5762a
$ hg stack
### topic: tools
### target: default (branch), 2 behind
s3$ Adding drill (unstable)
s2@ Adding saw (current)
s1: Adding hammer to the shopping list
s0^ add a pair of shoes (base)

One more to go:

$ hg next --evolve
move:[15] Adding drill
atop:[19] Adding saw
working directory now at bae3758e46bf
$ hg stack
### topic: tools
### target: default (branch), 2 behind
s3@ Adding drill (current)
s2: Adding saw
s1: Adding hammer to the shopping list
s0^ add a pair of shoes (base)

Let’s take a look at hg log once again:

$ hg log -G -r "s0::"
@  changeset:   20:bae3758e46bf
|  tag:         tip
|  topic:       tools
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     Adding drill
|
o  changeset:   19:d5c51ee5762a
|  topic:       tools
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     Adding saw
|
o  changeset:   18:b7509bd417f8
|  topic:       tools
|  parent:      12:fbff9bc37a43
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     Adding hammer to the shopping list
|
| o  changeset:   17:4cd7c1591a67
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  summary:     Adding orange juice
| |
| o  changeset:   16:20759cb47ff8
|/   parent:      12:fbff9bc37a43
|    user:        test
|    date:        Thu Jan 01 00:00:00 1970 +0000
|    summary:     Adding apple juice
|
o  changeset:   12:fbff9bc37a43
|  user:        test
~  date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     add a pair of shoes

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  12       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=12,
          pin=true,
          pos="1,12!",
          shape=circle,
          style=filled,
          width=1];
  16       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=16,
          pin=true,
          pos="1,16!",
          shape=circle,
          style=filled,
          width=1];
  12 -> 16         [arrowhead=none,
          penwidth=2.0];
  18       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=18,
          pin=true,
          pos="1,18!",
          shape=pentagon,
          style=filled,
          width=1];
  12 -> 18         [arrowhead=none,
          penwidth=2.0];
  17       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=17,
          pin=true,
          pos="1,17!",
          shape=circle,
          style=filled,
          width=1];
  16 -> 17         [arrowhead=none,
          penwidth=2.0];
  19       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=19,
          pin=true,
          pos="1,19!",
          shape=pentagon,
          style=filled,
          width=1];
  18 -> 19         [arrowhead=none,
          penwidth=2.0];
  20       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=20,
          pin=true,
          pos="1,20!",
          shape=pentagon,
          style=filled,
          width=1];
  19 -> 20         [arrowhead=none,
          penwidth=2.0];
}

Multi-headed stack

Stack is also very helpful when you have a multi-headed stack:

$ hg up s1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo "nails" > new_shopping
$ cat shopping >> new_shopping
$ mv new_shopping shopping
$ hg commit -m 'Adding nails'
$ hg stack
### topic: tools (2 heads)
### target: default (branch), 2 behind
s4: Adding drill
s3: Adding saw
s1^ Adding hammer to the shopping list (base)
s2@ Adding nails (current)
s1: Adding hammer to the shopping list
s0^ add a pair of shoes (base)

Solving this situation is easy with a topic: use merge or rebase. Merge within a multi-headed stack will use the other topic head as destination if the topic has two heads. But rebasing will yield a completely linear history so it’s what we will do.

$ hg log -G
@  changeset:   21:f936c6da9d61
|  tag:         tip
|  topic:       tools
|  parent:      18:b7509bd417f8
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     Adding nails
|
| o  changeset:   20:bae3758e46bf
| |  topic:       tools
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  summary:     Adding drill
| |
| o  changeset:   19:d5c51ee5762a
|/   topic:       tools
|    user:        test
|    date:        Thu Jan 01 00:00:00 1970 +0000
|    summary:     Adding saw
|
o  changeset:   18:b7509bd417f8
|  topic:       tools
|  parent:      12:fbff9bc37a43
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     Adding hammer to the shopping list
|
| o  changeset:   17:4cd7c1591a67
| |  user:        test
| |  date:        Thu Jan 01 00:00:00 1970 +0000
| |  summary:     Adding orange juice
| |
| o  changeset:   16:20759cb47ff8
|/   parent:      12:fbff9bc37a43
|    user:        test
|    date:        Thu Jan 01 00:00:00 1970 +0000
|    summary:     Adding apple juice
|
o  changeset:   12:fbff9bc37a43
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     add a pair of shoes
|
o  changeset:   11:f2d6cacc6115
|  parent:      5:2d50db8b5b4c
|  user:        test
|  date:        Thu Jan 01 00:00:00 1970 +0000
|  summary:     add a coat
|
o  changeset:   5:2d50db8b5b4c
|  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

strict digraph "Mercurial graph" {
  graph [rankdir=LR,
          splines=polyline
  ];
  node [label="\N"];
  0        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=0,
          pin=true,
          pos="1,0!",
          shape=circle,
          style=filled,
          width=1];
  3        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=3,
          pin=true,
          pos="1,3!",
          shape=circle,
          style=filled,
          width=1];
  0 -> 3   [arrowhead=none,
          penwidth=2.0];
  4        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=4,
          pin=true,
          pos="1,4!",
          shape=circle,
          style=filled,
          width=1];
  3 -> 4   [arrowhead=none,
          penwidth=2.0];
  5        [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=5,
          pin=true,
          pos="1,5!",
          shape=circle,
          style=filled,
          width=1];
  4 -> 5   [arrowhead=none,
          penwidth=2.0];
  11       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=11,
          pin=true,
          pos="1,11!",
          shape=circle,
          style=filled,
          width=1];
  5 -> 11  [arrowhead=none,
          penwidth=2.0];
  12       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=12,
          pin=true,
          pos="1,12!",
          shape=circle,
          style=filled,
          width=1];
  11 -> 12         [arrowhead=none,
          penwidth=2.0];
  16       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=16,
          pin=true,
          pos="1,16!",
          shape=circle,
          style=filled,
          width=1];
  12 -> 16         [arrowhead=none,
          penwidth=2.0];
  18       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
          label=18,
          pin=true,
          pos="1,18!",
          shape=pentagon,
          style=filled,
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  12 -> 18         [arrowhead=none,
          penwidth=2.0];
  17       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
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          label=17,
          pin=true,
          pos="1,17!",
          shape=circle,
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  16 -> 17         [arrowhead=none,
          penwidth=2.0];
  19       [fillcolor="#7F7FFF",
          fixedsize=true,
          group=default,
          height=1,
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          pin=true,
          pos="1,19!",
          shape=pentagon,
          style=filled,
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  18 -> 19         [arrowhead=none,
          penwidth=2.0];
  21       [fillcolor="#7F7FFF",
          fixedsize=true,
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          penwidth=2.0];
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          fixedsize=true,
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          pos="1,20!",
          shape=pentagon,
          style=filled,
          width=1];
  19 -> 20         [arrowhead=none,
          penwidth=2.0];
}

$ hg up s4
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg rebase
rebasing 19:d5c51ee5762a "Adding saw" (tools)
merging shopping
rebasing 20:bae3758e46bf "Adding drill" (tools)
merging shopping
$ hg stack
### topic: tools
### target: default (branch), 2 behind
s4@ Adding drill (current)
s3: Adding saw
s2: Adding nails
s1: Adding hammer to the shopping list
s0^ add a pair of shoes (base)

Collaborating through a non-publishing server

$ cd ..
$ hg clone server non-publishing-server
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd non-publishing-server
$ cat >> .hg/hgrc << EOF
> [phases]
> publish = false
> EOF
$ cd ..
$ hg clone server other-client
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd client

We can now share these draft changesets:

$ hg push ../non-publishing-server -r tools
pushing to ../non-publishing-server
searching for changes
adding changesets
adding manifests
adding file changes
added 4 changesets with 4 changes to 1 files (+1 heads)
8 new obsolescence markers

Pushing the new topic branch to a non-publishing server did not require –force. As long as new heads are on their own topic, Mercurial will not complain about them.

From another client, we will get them with their topic:

$ cd ../other-client
$ hg pull ../non-publishing-server
pulling from ../non-publishing-server
searching for changes
adding changesets
adding manifests
adding file changes
added 4 changesets with 4 changes to 1 files (+1 heads)
8 new obsolescence markers
new changesets b7509bd417f8:2d084ac00115 (4 drafts)
(run 'hg heads' to see heads)
$ hg topics --verbose
   tools (on branch: default, 4 changesets, 2 behind)
$ hg up tools
switching to topic tools
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg stack
### topic: tools
### target: default (branch), 2 behind
s4@ Adding drill (current)
s3: Adding saw
s2: Adding nails
s1: Adding hammer to the shopping list
s0^ add a pair of shoes (base)

We can also add new changesets and share them:

$ echo screws >> shopping
$ hg commit -A -m "Adding screws"
$ hg push ../non-publishing-server
pushing to ../non-publishing-server
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files

And retrieve them from the first client:

$ cd ../client
$ hg pull ../non-publishing-server
pulling from ../non-publishing-server
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets 0d409663a1fd (1 drafts)
(run 'hg update' to get a working copy)
$ hg update
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg stack
### topic: tools
### target: default (branch), 2 behind
s5@ Adding screws (current)
s4: Adding drill
s3: Adding saw
s2: Adding nails
s1: Adding hammer to the shopping list
s0^ add a pair of shoes (base)

«  Terminology of the obsolete concept   ::   Contents   ::   Initial setup  »