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<html>
<head>
<title>Implementing Development Policies</title>
</head>
<body>
<a name="Implementing_Development_Policies"></a>
<a href="http://www.regexps.com">The Hackerlab at <code>regexps.com</code></a>
<h2 align=center>Implementing Development Policies</h2>
<small>
<b>up: </b><a href="arch.html#arch">arch</a></br>
<b>next: </b><a href="theory-of-patches.html#The_Theory_of_Patches_and_Revisions">The Theory of Patches and Revisions</a></br>
<b>prev: </b><a href="getting-started.html#Getting_Started_with_arch">Getting Started with arch</a></br>
</small>
<br>
<p>Different projects have different policies for managing the "main
development path" as distinguished from various kinds of release
(such as candidate releases, experimental releases, and stable
releases).
</p><p><code>arch</code>
is flexible enough to allow many such policies to be
implemented in a direct way. Here are some examples and hints about
using <code>arch</code>
.
</p>
<a name="Milestone/Numbered_Versions"></a>
<h3 align=center>Milestone/Numbered Versions</h3>
<p>One development policy is based on <em>
<a name="index-pt:0"></a>
milestones
</em>
. The team works on
one milestone goal at a time. When they have just about reached that
milestone, they make <em>
<a name="index-pt:1"></a>
candidate releases
</em>
of the milestone for people
to test. After fixing bugs, a <em>
<a name="index-pt:2"></a>
milestone release
</em>
is made.
</p><p>After several milestones, the milestone release gets a version number,
and becomes a <em>
<a name="index-pt:3"></a>
version release
</em>
.
</p><p>Beginning from scratch on the first milestone, the developers create
the first development path -- in which to work on reaching the
first milestone:
</p><pre>
mozilla--devo--1.0
------------------
base-0
patch-1
patch-2
patch-3
patch-4
</pre>
<p>After some time, they are ready to make some candidate releases
and enter a bug-fixing cycle. They'll use tags for that -- making the
bug fixes in the <code>devo</code>
branch:
</p><pre>
mozilla--devo--1.0
------------------
base-0
patch-1
patch-2 mozilla--milestone--1.0
patch-3 -----------------------
patch-4 --------------------->base-0 (tag -- 1st release candidate)
patch-5 .------>patch-1 (tag -- 2nd candidate)
patch-6 -------------- ---->patch-3 (tag -- 3rd candidate)
patch-7 |
patch-8 ----------------
</pre>
<p>In the diagram, patches <code>5..8</code>
in the <code>devo</code>
branch are fixes made
based on reports from candidate releases. We'll suppose that after
<code>patch-8</code>
, the first milestone appears to be stable. The developers
want to make the milestone release, and begin work on milestone <code>2</code>
:
</p><pre>
mozilla--devo--1.0
------------------
base-0
patch-1
patch-2 mozilla--milestone--1.0
patch-3 -----------------------
patch-4 --------------------->base-0 (tag -- 1st release candidate)
patch-5 .------>patch-1 (tag -- 2nd candidate)
patch-6 -------------- ---->patch-3 (tag -- 2rd candidate)
patch-7 | version-0 (milestone release)
--patch-8 ----------------
|
| mozilla--devo--2.0 (development path for the second milestone)
| ------------------
->base-0 (continuation)
</pre>
<p>That pattern can continue indefinately, eventually resulting in a
versioned release, (again using tags):
</p><pre>
mozilla--devo--1.0 mozilla-milestone--1.0
------------------ ----------------------
...
--patch-N---------------------->...
| version-0 (milestone 1 release)
|
|
| mozilla--devo--2.0 mozilla-milestone--2.0
| ------------------ ----------------------
| ...
->patch-N---------------------->...
| version-0 (milestone 2 release)
|
|
| mozilla--devo--3.0 mozilla-milestone--3.0
| ------------------ ----------------------
| ...
->patch-N---------------------->...
| version-0 (milestone 3 release)
| ...
|
| mozilla--devo--10.0 mozilla-milestone--10.0
| ------------------- -----------------------
| ...
->patch-N---------------------->...
--version-0 (milestone 10 release)
|
| mozilla-1.0
| -----------
->base-0 (tag)
version-0 (versioned release)
</pre>
<p>That pattern of <code>arch</code>
usage is very simple because the developers
stay in sync, following a strict cycle of working on a milestone,
making candidate releases and bug-fixing, making a milestone releases
and starting on the next milestone. Less synchronized development
can be much more complicated, as illustrated in the next example:
</p>
<a name="Even/Odd_Versions"></a>
<h3 align=center>Even/Odd Versions</h3>
<p>Another, more intricate policy is based on version numbers. Odd
numbered versions are the "leading-edge" of development -- often
unstable, but having the very latest sources. Even numbered versions
are "stable" -- lagging behind the leading-edge, but containing only
code known to work reasonably well.
</p><p>The <code>arch</code>
concept of a "continuation version" is ideal for this,
because there is no requirement that a continuation version be a
continuation of the immediately preceeding version.
</p><p>A series of diagrams can help to illustrate this usage of <code>arch</code>
and
some of the subtleties that can arise. We'll start with just
the initial leading-edge development path
</p><pre>
linux--0.1
----------
base-0
patch-1
patch-2
patch-3
patch-4
version-0
</pre>
<p>At that point, the developers decide to make the first stable release:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 |
patch-4 |
version-0 ------
</pre>
<p>We can suppose that <code>patch-1</code>
of <code>linux--0.2</code>
is just a quick change
to the top level <code>README</code>
file, and that after that -- the new stable
version is sealed (creating <code>version-0</code>
) and released. We never
particularly want to merge <code>patch-1</code>
of <code>linux-0.2</code>
back on to the
odd-numbered versions.
</p><p>Naturally, some bugs are detected in the stable release -- three in
rapid succession. The developers fix these on the <em>leading edge</em>
branch, planning to merge them with the stable tree later:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 |
patch-4 |
version-0 ------
versionfix-1
versionfix-2
versionfix-3
</pre>
<p>They wait a week for some testing to occur. The bug fixes are looking
ok, so the developers decide to start work on the next leading-edge
version:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 |
patch-4 |
version-0 ------
versionfix-1
versionfix-2
--versionfix-3
|
|
| linux--0.3
| ---------
->base-0 (continuation)
patch-1
</pre>
<p>Just as the developers are about to merge the bug fixes with the
stable version, one more bug report trickles in. Fortunately, it's a
trivial bug -- so the developers are confident about making the fix in
the leading edge, but immediately releasing it in the stable version.
</p><p>Here's a catch, though -- the latest leading edge version
(<code>linux--0.3</code>
) has already diverged from the stable version because of
<code>patch-1</code>
. The developers definately don't want <code>patch-1</code>
of <code>0.3</code>
in
the the stable <code>0.2</code>
yet, so they fix the newly reported bug in <code>0.1</code>
,
then merge all four bug fixes with the stable tree in the usual way.
Meanwhile, separate work also continues on <code>0.3</code>
:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 | ->versionfix-1 (merge)
patch-4 | |
version-0 ------ |
versionfix-1\ |
versionfix-2 |-------
--versionfix-3 |
| versionfix-4/
|
|
|
| linux--0.3
| ---------
->base-0 (continuation)
patch-1
patch-2
patch-3
</pre>
<p>It's worth noting at that point that <code>linux--0.3</code>
is missing a bug-fix
(<code>versionfix-4</code>
) from <code>linux--0.1</code>
:
</p><pre>
% cd ~/wd/linux--0.3
</pre>
<pre>
% larch whats-missing linux--0.1
versionfix-4
</pre>
<p>We'll eventually do an update to pick up that bug fix, but first,
let's make the situation more complicated.
</p><p>Suppose, some mailing lists get wind of <code>patch-3</code>
in <code>linux--0.3</code>
.
Soon <code>Slashdot</code>
and <code>Newsforge</code>
pick up the story. It turns out that
<code>patch-3</code>
is a very desirable feature and the implementation appears
to be clean and stable. People are clammering for its appearence in a
stable release, and the developers happen to think it is a good idea.
</p><p>So, they start the next stable revision:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 | ->versionfix-1 (merge)
patch-4 | | |
version-0 ------ | |
versionfix-1\ | |
versionfix-2 |------- | linux--0.4
--versionfix-3 | | ----------
| versionfix-4/ --->base-0 (continuation)
|
|
|
| linux--0.3
| ---------
->base-0 (continuation)
patch-1
patch-2
patch-3
</pre>
<p>They only want <code>patch-3</code>
of <code>0.3</code>
for <code>0.4</code>
-- not anything else.
That's a job for <code>replay --exact</code>
:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 | ->versionfix-1 (merge)
patch-4 | | |
version-0 ------ | |
versionfix-1\ | |
versionfix-2 |------- | linux--0.4
--versionfix-3 | | ----------
| versionfix-4/ --->base-0 (continuation)
| =->patch-1 (replay --exact merge)
| | version-0
| .
| linux--0.3 |
| --------- .
->base-0 (continuation) |
patch-1 .
patch-2 |
patch-3-=--=--=--=--=--=--=-
...
</pre>
<p>After merging the much-desired <code>patch-3</code>
of <code>0.3</code>
into <code>0.4</code>
, the
developers seal <code>0.4</code>
and make the stable release.
</p><p>Let's suppose that development on <code>0.3</code>
continues for a while.
After some time, the developers decide that <code>0.3</code>
has aquired enough
new features. They want to do two things: start <code>0.5</code>
, and start
getting the stable <code>0.6</code>
release ready:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 | ->versionfix-1 (merge)
patch-4 | | |
version-0 ------ | |
versionfix-1\ | |
versionfix-2 |------- | linux--0.4
--versionfix-3 | | ----------
| versionfix-4/ --->base-0 (continuation)
| =->patch-1 (replay --exact merge)
| | version-0
| .
| linux--0.3 |
| --------- .
->base-0 (continuation) |
patch-1 .
patch-2 |
patch-3-=--=--=--=--=--=--=-
... linux--0.6
-version-0 ----------
|
|
|
| linux--0.5
| ----------
->base-0
</pre>
<p>Notice that they haven't created the base revision for <code>0.6</code>
yet.
There's a choice here. They could make <code>0.6</code>
a continuation of <code>0.4</code>
,
then merge in all the patches they're missing from <code>0.3</code>
. On the
other hand, they could make <code>0.6</code>
a continuation of some <code>0.3</code>
and
pick up all those missing patches "the easy way".
</p><p>But, oops, when someone checks out <code>version-0</code>
from <code>0.3</code>
and runs
<code>whats-missing</code>
, they find out that the <code>0.3</code>
branch never picked up
<code>versionfix-4</code>
from <code>0.1</code>
. That's easily fixed by updating a <code>0.3</code>
tree against <code>0.1</code>
, and checking in the resulting merge to <code>0.3</code>
.
The resulting merge is also the revision that will become the base
revision for <code>0.6</code>
:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 | ->versionfix-1 (merge)
patch-4 | | |
version-0 ------ | |
versionfix-1\ | |
versionfix-2 |------- | linux--0.4
--versionfix-3 | | ----------
| versionfix-4/ --->base-0 (continuation)
| | =->patch-1 (replay --exact merge)
| ----- | version-0
| | .
| linux--0.3 | |
| --------- | .
->base-0 (continuation) |
patch-1 | .
patch-2 | |
patch-3-=--=--=--=--=--=--=-
... | linux--0.6
-version-0 V ----------
| versionfix-1 (0.1 update)------>base-0 (continuation)
| version-0
|
| linux--0.5
| ----------
->base-0
patch-1
patch-2
</pre>
<p>Meanwhile, new work continues on <code>0.5</code>
.
</p><p>But now, the <code>0.5</code>
tree is in an interesting state. If a developer
checks out the latest <code>0.5</code>
and asks:
</p><pre>
% larch whats-missing linux--0.1
linux--0.1--versionfix-4
</pre>
<p>If the developer asks <code>whats-missing</code>
from <code>0.3</code>
, the answer is:
</p><pre>
% larch whats-missing linux--0.3
linux--0.3--versionfix-1
</pre>
<p>If those two patches were unrelated -- there would be no problem:
simply update from both branches and check the result into <code>0.5</code>
.
</p><p>In fact, though, <code>versionfix-1</code>
from <code>0.3</code>
is really the same change
as <code>versionfix-4</code>
from <code>0.1</code>
(look back at how <code>versionfix-1</code>
was
created). Let's also suppose that when the fix was merged into <code>0.3</code>
,
a slight change had to be made -- to resolve a merge conflict.
</p><p>So if the developer just blindly updates from <code>0.1</code>
, then from <code>0.3</code>
,
the second update will result in new conflicts. That might not be so
bad if we're only talking about two patches -- but if we were talking
about <code>20</code>
or <code>200</code>
, a lot of needless work would be called for.
</p><p>Fortunately, <code>arch</code>
can help. First, the developer gets the latest
<code>0.5</code>
revision:
</p><pre>
% larch get linux--0.5 ~/wd/linux--0.5
</pre>
<p>Then gets a list of all patches missing from <code>0.1</code>
and <code>0.3</code>
:
</p><pre>
% cd ~/wd/linux--0.5
</pre>
<pre>
% larch whats-missing --full linux--0.1 linux--0.3
archive@kernel.org--primary/linux--0.1--versionfix-4
archive@kernel.org--primary/linux--0.3--versionfix-1
</pre>
<p>That list can be piped into the <code>reconcile</code>
tool:
</p><pre>
% ... | larch reconcile
archive@kernel.org--primary/linux--0.3--versionfix-1
</pre>
<p>What happened? <code>reconcile</code>
figured out that <code>versionfix-1</code>
from
<code>0.3</code>
already includes <code>versionfix-4</code>
from <code>0.1</code>
-- there's no need to
apply both patches. So <code>patch-plan</code>
reported the list of patches
that <em>do</em> need to be applied, and in this case, there's only one.
</p><p>In a more complicated situation, <code>patch-plan</code>
would print a list of
patches in the order they should be applied. In general, it will be a
subset of the patches in its input, but applying that subset will have
the same effect as applying all of the patches (but hopefully with
fewer conflicts).
</p><p>The developer uses <code>larch replay --list</code>
to process that list, finally
winding up with:
</p><pre>
linux--0.1 linux--0.2
---------- ----------
base-0 ----> base-0 (continuation)
patch-1 | patch-1
patch-2 | version-0
patch-3 | ->versionfix-1 (merge)
patch-4 | | |
version-0 ------ | |
versionfix-1\ | |
versionfix-2 |------- | linux--0.4
--versionfix-3 | | ----------
| versionfix-4/ --->base-0 (continuation)
| | =->patch-1 (replay --exact merge)
| ----- | version-0
| | .
| linux--0.3 | |
| --------- | .
->base-0 (continuation) |
patch-1 | .
patch-2 | |
patch-3-=--=--=--=--=--=--=-
... | linux--0.6
-version-0 V ----------
| versionfix-1 (0.1 update)------>base-0 (continuation)
| | version-0
| |
| linux--0.5 |
| ---------- |
->base-0 |
patch-1 |
patch-2 V
patch-3 (0.1/0.3 reconciliation)
</pre>
<p>Now if someone gets the latest revision of <code>0.5</code>
and asks:
</p><pre>
% larch whats-missing --full linux--0.1 linux--0.3
[no output]
</pre>
<p>Isn't <code>reconcile</code>
handy?
</p>
<small><i>arch: The arch Revision Control System
</i></small><br>
<a href="http://www.regexps.com">The Hackerlab at <code>regexps.com</code></a>
</body>
|
