Subversion

Tricode Professional Serviceswww.tricode.nl

22-08-2008Patrick van Dissel

Index

• What is Subversion (SVN)?

• Subversion features– Repository based versioning– Metadata Properties– Distinction Between Status and Update– Conflict Resolution– Updates and Commits are Separate

• Standard project structure

• Development/Release workflow

• Tips

• An improved version of CVS– Uses a filesystem tree;

everything works the same way, everything is versioned(files, directories, renames, deletions, properties, …)

• Branches and Tags work exactly the same as the Trunk, everything has it’s place in the repository filesystem tree

• Repositories/Modules can connect to each other, like a symbolic-link in a *nix filesystem

• A revision contains a complete state of the repository filesystem tree

– Minimized network traffic• only connects to the repository when really needed• tranfers are based on differences between versions instead of

sending whole files

What is Subversion (SVN)?

Terms of how they improve upon CVS's design

• Directory versioning– CVS only tracks the history of individual files, but Subversion

implements a “virtual” versioned filesystem that tracks changes to whole directory trees over time. Files and directories are versioned

• True version history– Since CVS is limited to file versioning, operations such as copies and

renames—which might happen to files, but which are really changes to the contents of some containing directory—aren't supported in CVS. Additionally, in CVS you cannot replace a versioned file with some new thing of the same name without the new item inheriting the history of the old—perhaps completely unrelated—file. With Subversion, you can add, delete, copy, and rename both files and directories. And every newly added file begins with a fresh, clean history all its own

• Versioned metadata– Each file and directory has a set of properties—keys and their values

—associated with it. You can create and store any arbitrary key/value pairs you wish. Properties are versioned over time, just like file contents

Subversion features (1)

Terms of how they improve upon CVS's design

• Atomic commits– A collection of modifications either goes into the repository

completely, or not at all. This allows developers to construct and commit changes as logical chunks, and prevents problems that can occur when only a portion of a set of changes is successfully sent to the repository

• Consistent data handling– Subversion expresses file differences using a binary differencing

algorithm, which works identically on both text (human-readable) and binary (human-unreadable) files. Both types of files are stored equally compressed in the repository, and differences are transmitted in both directions across the network

• Efficient branching and tagging– The cost of branching and tagging need not be proportional to the

project size. Subversion creates branches and tags by simply copying the project, using a mechanism similar to a hard-link. Thus these operations take only a very small, constant amount of time

Subversion features (2)

Repository based versioning

A revision contains a complete state of the repository filesystem tree

Revision numbering =>

CVS uses file based versioning, SVN uses repository based versioning.

Metadata properties

rev.1 svn:ignore *.tmpsvn:keywords Id

rev.2 svn:ignore *.tmpsvn:ignore ~*svn:keywords Id

CVS uses .cvsignore files containing patterns of files/directories to exclude from CVS.

In SVN, every file and directory can have metadata properties.SVN recognizes the following special properties but will store any arbitrary properties set:

Metadata Properties

- svn:ignore- svn:keywords

- URL, HeadURL- Author, LastChangedBy- Date, LastChangedDate- Rev, Revision, LastChangedRevision- Id

- svn:executable- svn:eol-style One of 'native', 'LF', 'CR', 'CRLF‘- svn:mime-type- svn:externals- svn:needs-lock If present, indicates that the file should be locked

before it is modifiedNote: The svn:keywords, svn:executable, svn:eol-style, svn:mime-type and svn:needs-lock properties cannot be set on a directory. A non-recursive attempt will fail.

Metadata Properties – Usage (1)- svn:ignore A newline separated list of file patterns to ignore

For example:svn ps svn:ignore * cache

This excludes all files within the cache directory from adding to SVN. Files still can be added by specifically adding them

- svn:keywords Keywords to be expanded (case-sensitive!)

For example:svn ps -R svn:keywords Id .

This sets the ‘Id’ keyword on all files recursively from current directory. After this, ‘$Id$’ will be replaced at commit with

information of the last modification and looks something like: $Id: calc.c 148 2006-07-28 21:30:43Z sally $

Metadata Properties – Usage (2)- svn:externals A newline separated list of module specifiers

For example: Zend http://svn.tri...work/tags/1.5.2-tricode/library/Zend/ Tricode http://svn.tri.../tricode/branches/1.1/library/Tricode/

This connects the Zend directory to the specified 1.5.2-tricode repository and the Tricode directory to specified 1.1 branch.

When you update your whole project, the externalswill also be updated.

When you commit your while project, the externalswill NOT be committed. Commits to externals must be done explicitly.

• One of the fundamental rules of Subversion is that a “push” action does not cause a “pull”, nor the other way around.

– Just because you're ready to commit new changes to the repository doesn't mean you're ready to receive changes from other people

– And if you have new changes still in progress, then svn update should gracefully merge repository changes into your own, rather than forcing you to publish them

Updates and Commits are Separate

• svn status– Shows only information about current working-copy

without needing to connect to the repository.

Unless you specify the -u option, then the reposity is contacted to recieve update information (files are not updated!)

• svn update– Updates current working-copy to the latest/given

revision and shows information about the files that are updated

Distinction Between Status and Update

Steps for merging:1. Open the project/working-copy you want to merge

changes to

For merging the ‘trunk’ to ‘cycle18’ branche, you open the ‘cycle18’ branche and then execute the `svn merge` on the {trunk url}

2. Make shure you have NO local modifications (`svn status`)

3. Execute merge

4. Solve conflicts & mark resolved

5. Commit changes to complete merge

Merging

• {projectname}– branches => specific development versions– tags => released versions– trunk => latest development version

Naming conventionFor branches:• YYYY-MM-DD_I#####• YYYY-MM-DD_RFS###• YYYY-MM-DD_RFC###• YYYY-MM-DD_cycle##For tags:• YYYY-MM-DD_cycle##

Standard project structure

• {projectname}– branches

• 2008-08-18_cycle18• 2008-08-19_I7654321• 2008-08-19_RFC0012345• 2008-08-19_RFC0022386• 2008-08-19_RFS0012345

– tags• 2008-08-18_cycle17

– trunk

Standard project structure

Development/Release workflow

FA TA Build UAT

1 week 1 week 1 week 1 week

trunk (prod + incidents/rfs)

GoLive

After GoLiveprevious cycle

Create cyclebranch

Merge to cycle

Merge to cycle

NOKFix NOK RFC

Branch

Create branchper Change Build Changes Decide which Changes

will go in the release

Tag

Cleanbranches

Development/Release workflowDEV TEST LIVE

/virtual/{project} /virtual/{project} /virtual/{project}

../trunk

../b1

../ixxx

../trunk

../b1trunksymbolic-link

switcher

cronAuto remove brancheswhich are not in HEADSVN revision

symbolic-link

• Use JIRA issue keys in commit messages– If a commit is resolving an issue from the issue

tracker, the issue KEY should be indicated in the commit comment (i.e. "This resolves ZF-2")

• Enable SVN Auto-props in SVN client config– Config can be found at:

%UserProfile%\Application Data\Subversion\config– Set the following in the config:

enable-auto-props = yes[auto-props]*.php = svn:keywords=Id 

Tips