Vendor Branches

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Vendor Branches in Mercurial:

Elegant Management of Third-Party Code

Martin Geisler

[email protected]

Mercurial Geek Night IINovember 24th, 2010


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Outline

Introduction

Using MercurialWorkflowsBranches

Vendor BranchesVendor Branches in MercurialHandling Renamed Files

Wrapping Up

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Outline

Introduction



Wrapping Up

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What is Mercurial?

Main features:

fast,distributedrevision control system

robust support for branchingandmerging

very flexible and extensible

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Who is Using it?

Mercurial is used by:

Oracle for Java, OpenSolaris, NetBeans, OpenOffice, . . .

Mozilla for Firefox, Thunderbird, . . .

Google

many more. . .

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Centralized Revision Control

Single repository, multiple working copies:

Repository

hello.cMakefile

Alice

goodbye.cMakefile

Bob

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Centralized Revision Control

Single repository, multiple working copies:

Repository

hello.cMakefile

Alice

goodbye.cMakefile

Bob

Drawbacks:

network latency single point of failure

contrained workflow

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Distributed Revision Control

Mercurial duplicates the history on many servers:

Alice Bob

hello.cMakefile

goodbye.cMakefile

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Distributed Revision Control

Mercurial duplicates the history on many servers:

Alice Bob

hello.cMakefile

goodbye.cMakefile

Advantages: no network latency

distributed, off-line operations no imposed workflow

Drawback(?):

must synchronize repositories

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Moving Changesets Around

Pull and merge:

I

Alice

I

Bob

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Pull and merge:

I

Alice

A1 I

Bob

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Pull and merge:

I

Alice

A1 A2 I

Bob

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Pull and merge:

I

Alice

A1 A2 I

Bob

B1

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Pull and merge:

I

Alice

B1

A1 A2 I

Bob

B1pull

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Pull and merge:

I

Alice

B1

A1 A2 A3 I

Bob

B1

merge

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Pull and merge:

I

Alice

B1

A1 A2 A3 I

Bob

B1

Merging: find common ancestor of A2 and B1: I

compute differences between I and B1

apply them to A2, taking renames into account

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C


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Key Mercurial Commands

Alice

hello.cMakefile

commit

update

Local commands:

hg commit: save a snapshot into the current repository

hg update: checkout revision into working directory

hg merge: join different lines of history

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K M i l C d


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Key Mercurial Commands

Alice

hello.cMakefile

commit

update

push

pull

Local commands:

hg commit: save a snapshot into the current repository

hg update: checkout revision into working directory

hg merge: join different lines of history

Network commands:

hg pull: retrieve changesets from another repository

hg push: send your changesets to another repository

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O li


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Outline

Introduction



Wrapping Up

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O tli


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Outline

Introduction



Wrapping Up

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W kfl i T


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Workflow in a Team

Mercurial scales from a single team. . . :

Alice

Bob

Carla Test Prod

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Workflow Between Two Computers


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Workflow Between Two Computers

. . . to working with yourself:

AlicesDesktop

AlicesLaptop

bitbucket.org

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Outline


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Outline

Introduction



Wrapping Up

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Release Branches


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Release Branches

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Release Branches


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Release Branches

1.0

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Release Branches


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Release Branches

1.0

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Release Branches


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Release Branches

1.0

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Release Branches


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Release Branches

1.0

1.0.1

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Release Branches


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Release Branches

1.0

1.0.1

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Release Branches


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Release Branches

1.0

1.0.1

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Release Branches


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1.0

1.0.1 1.0.2

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Release Branches


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1.0

1.0.1 1.0.2

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Outline


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Introduction



Wrapping Up

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The Library Maintenance Problem


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The situation:

your application bundles libfoo version1.0

you discover and fix a bug in libfoo later, libfoo version2.0is released

what now?

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The situation:



what now?

The problem:

there might be many files in libfoo

you might have changed several of them

your changes were spread over many commits

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The situation:



what now?

The problem:




you might have changed libfoo when you imported it

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The situation:



what now?

The problem:




you might have changed libfoo when you imported it

files wererenamedin libfoo 2.0!

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Handling Library Upgrades


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The goal:

make the same fixes to libfoo 2.0 as you did to 1.0

Vendor branches help you here: gives you clear distinction between

changes made by the vendor your own changes

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Outline


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Introduction



Wrapping Up

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Vendor Branches in Mercurial


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High-level view of vendor branches:

default:

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default:

libfoo:

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default:

libfoo:

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default:

libfoo:

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default:

libfoo:

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default:

libfoo:

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default:

libfoo:

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default:

libfoo:

This workflow lets you:

clearly distinguish between upstream code and your code

directly modify libraries in your codebase

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H h l l f d b h


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default:

libfoo:

This workflow lets you:

clearly distinguish between upstream code and your code

directly modify libraries in your codebase Mercurial knows exactly what to merge

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What Happens in a Merge?

O Wh d di ib d i i l k?


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Or: Why does distributed revision control work?

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O Wh d di t ib t d i i t l k?


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O Wh d di t ib t d i i t l k?


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local head

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local head

remote head

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local head

remote head

commonancestor

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local head

remote head

commonancestor

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local head

remote head

commonancestor

1

2

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local head

remote head

commonancestor

1

2

1 +2

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Merging Vendor Branches

Upgrading from libfoo version 1 0 to version 2 0:


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Upgrading from libfoo version 1.0 to version 2.0:

default:

libfoo:

. . .

. . . 1.0

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default:

libfoo:

. . .

. . . 1.0

hg update libfoo

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default:

libfoo:

. . .

. . . 1.0

hg update libfoo

unpack and import libfoo version 2.0

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pg g

default:

libfoo:

. . .

. . . 1.0 2.0

hg update libfoo


hg commit -m Import of libfoo 2.0

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pg g

default:

libfoo:

. . .

. . . 1.0 2.0

hg update libfoo



hg update default

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pg g

default:

libfoo:

. . .

. . . 1.0 2.0

local head

remote headcommonancestor

hg update libfoo



hg update default

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default:

libfoo:

. . .

. . . 1.0 2.0

local head


hg update libfoo



hg update default

hg merge libfoo

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default:

libfoo:

. . .

. . . 1.0 2.0

local head


hg update libfoo



hg update default

hg merge libfoo

hg commit -m Merged with libfoo 2.0

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Outline


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Introduction



Wrapping Up

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Importing a Code Drop

Mercurial can help you:


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$ rm -r lib/libfoo

$ unzip libfoo-2.0.zip -d lib/libfoo

$ hg status

M lib/libfoo/modified.txt

! lib/libfoo/deleted.txt

? lib/libfoo/new.txt

Question: has deleted.txt been renamed to new.txt?$ hg addremove --similarity 90

removing deleted.txt

adding new.txt

recording removal of deleted.txt as rename to new.txt (94% similar)

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Finding Renamed Files

Tracking renames is important:


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you fix a bug in X.java in version 1.0

version 2.0 now uses Y.java instead of Y.java Mercurial does the right thing with rename tracking

public class X {

static int

theAnswer = 41;

}

X.java

public class Y {

static int

theAnswer = 41;

}

Y.java

public class X {

static int

theAnswer = 42;

}

X.java

public class Y {

static int

theAnswer = 42;

}

Y.java

rename

bugfix

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Outline


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Introduction



Wrapping Up

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More Information

Mercurial homepage:htt // i l l i /
http://mercurial.selenic.com/http://mercurial.selenic.com/


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http://mercurial.selenic.com/

Mercurial: The Definitive Guide:http://hgbook.red-bean.com/

Getting Started:http://mercurial.aragost.com/kick-start/

http://mercurial.ch/

http://hginit.com/ Some free Mercurial hosting sites:

http://bitbucket.org/

http://code.google.com/

http://sourceforge.net/

http://www.codeplex.com/

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Contact

Please get in touch if you have more questions or have consideredusing Mercurial in your organization:
http://mercurial.selenic.com/http://hgbook.red-bean.com/http://mercurial.aragost.com/kick-start/http://mercurial.ch/http://hginit.com/http://bitbucket.org/http://code.google.com/http://sourceforge.net/http://www.codeplex.com/http://www.codeplex.com/http://sourceforge.net/http://code.google.com/http://bitbucket.org/http://hginit.com/http://mercurial.ch/http://mercurial.aragost.com/kick-start/http://hgbook.red-bean.com/http://mercurial.selenic.com/


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using Mercurial in your organization:

Email: [email protected]

IRC: mgin #mercurial on irc.freenode.net

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Mercurial Contributors

From http://ohloh.net/p/mercurial/map:
http://localhost/var/www/apps/conversion/tmp/scratch_6/[email protected]://localhost/var/www/apps/conversion/tmp/scratch_6/mghttp://localhost/var/www/apps/conversion/tmp/scratch_6/#mercurialhttp://localhost/var/www/apps/conversion/tmp/scratch_6/irc.freenode.nethttp://localhost/var/www/apps/conversion/tmp/scratch_6/irc.freenode.nethttp://localhost/var/www/apps/conversion/tmp/scratch_6/#mercurialhttp://localhost/var/www/apps/conversion/tmp/scratch_6/mghttp://localhost/var/www/apps/conversion/tmp/scratch_6/[email protected]://ohloh.net/p/mercurial/maphttp://ohloh.net/p/mercurial/maphttp://ohloh.net/p/mercurial/map


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Mercurial Contributors

From http://ohloh.net/p/mercurial/map:
http://ohloh.net/p/mercurial/maphttp://ohloh.net/p/mercurial/maphttp://ohloh.net/p/mercurial/map


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Thank you!Thank you!

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