#pragma section-numbers 2

<<Include(A:dev)>>
<<Include(A:historic)>>


= Poisoned Changesets =

'''Status: abandoned'''

'''Proponent: MartinGeisler'''

Original proposal: [[http://markmail.org/message/vyyjfyshhnb5acpc|RFC: dealing with dead, anonymous feature branches]]

Implementation of proposal: [[http://bitbucket.org/mg/dead-branches]]

== Definitions ==

We will use the following definitions:

 poisoned changeset:: a changeset with `poisoned=1` in its `extra` dict.

 dead head:: a poisoned changeset that is also a head.

 dead changeset:: a changeset from which you can only reach dead heads.

 dead branch:: a set of dead changesets

== Rules for Push ==

When pushing changesets, the following two rules are observed:

 1. First, send changesets that are not on a dead branch.

 2. Then, send changesets descending from what is now remote heads.

The discovery protocols gives us the heads of the common set of nodes. From these we can compute the changesets that are not on a dead branch (rule 1). We can then look at the remaining heads among the nodes in the common set and push descendants of these.

No new information is neede by this protocol, everything can be computed locally from information about the common set of nodes.

== Rules for Pull ==

Symmetric to push, but the server needs to filter the changesets.

== Use Cases ==

An experiment can be stopped, whether it has been pushed to another server or not:

{{{#!dot
digraph {
  graph [rankdir = LR]
  node [shape = box, style = filled, fillcolor = cornflowerblue]
  A -> B;
}
}}}

A new commit is made:

{{{#!dot
digraph {
  graph [rankdir = LR]
  node [shape = box, style = filled, fillcolor = cornflowerblue]
  A -> B -> X;
}
}}}

A pull is made, bringing ind `C`, `D`, and `E` and it is decided that `X` is no longer is relevant:

{{{#!dot
digraph {
  graph [rankdir = LR]
  node [shape = box, style = filled, fillcolor = cornflowerblue]
  Y [fillcolor = FireBrick]

  A -> B -> C -> D -> E;
  B -> X-> Y;
}
}}}

== See Also ==

 * ChangesetEvolution

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CategoryDeveloper CategoryOldFeatures