versiebeheer op bestanden met Subversion

LaQuSoLaboratory for Quality Software

versiebeheer op bestandenmet

Subversion

HG 5.9128 september 2009

Reinier Post


Subversion

is softwarevoor versiebeheer

op directory trees (mapstructuren?) met bestanden.

http://subversion.tigris.org/


versiebeheer op bestanden

Multiple versions of a file: for example• a document you’re editing + a backup copy• your document at home + a copy at work• your version of a document + Harry’s version• a copy of a webpage + the version you modified with your

suggestions


version control on whole directory trees

Multiple versions of directory trees full of files:• a website• a LaTeX document (single author or co-authored)• the source code of a computer program• a user software profile (config files, startup scripts, utilities)


demo 0: find some exampleslocate .oud; locate .oldlocate /home | grep -v '[~%v]$' | ~rp/bin/previsprefix

most files are completely redundant - not worth saving!• local copies of available files copied from elsewhere• files generated by programs from other files• temporary backup copies

different versions of the same file: only partially redundant=> version control problem: what to save, when, and where?


demo 1: diff

locate /home/rp | grep -v '[~%v]$' | fgrep -v rpsoft | previsprefixdiffdiff –udiff –r

diff• is a standard Unix tool (since the 70s)• only useful on plain text files, including structured plaintext

(source code, XML , etc.) if formatted uniformly

http://unixhelp.ed.ac.uk/CGI/man-cgi?diff

http://unixhelp.ed.ac.uk/CGI/man-cgi?locate

http://unixhelp.ed.ac.uk/CGI/man-cgi?grep

http://unixhelp.ed.ac.uk/CGI/man-cgi?fgrep

http://www.win.tue.nl/~rp/util/previsprefix


demo 2: patch

diff –u a a.modified > a.diffrm a.modifiedpatch < a.diff # turns a into a.modified !

patch• is a standard Unix tool (since the late 80s)• only applicable when you can work with diffs• allows “merging” different changes into single result

http://archives.real-time.com/pipermail/cocoon-devel/2000-November/003477.html

http://unixhelp.ed.ac.uk/CGI/man-cgi?rm

http://www.gnu.org/software/patch/patch.html

http://en.wikipedia.org/wiki/Patchhttp://groups.google.com/groups?selm=1508%40sdcrdcf.UUCP


RCS: version control on a file

• let user explicitly commit versions of a file• remember all versions the user doesn’t remove• be “clever”: save the diffs!• every version has a number• every version has an (optional) log message• RCS can record info about the version in the file• written in 1985, soon very popular

http://www.cs.purdue.edu/homes/trinkle/RCS/

http://citeseer.nj.nec.com/tichy91rcs.html


demo 3: RCS

locate /home/rp | grep RCS # on win.tue.nl Solaris/Linux# examine a ,v file, you’ll see they are diffs

main RCS commands:• ci file # check current version of file in to file,v

• co file # check latest version of file out from file,v

• rcsdiff file # diff file with latest version in file,v


the power of RCS

On a file in RCS you can ask questions like:• is this copy the latest “good” version? • to which “good” version (created when) does this

copy correspond, if any?• what are the diffs between June 1st and today?• is the copy I mailed to Harry older or newer

than the copy on the website?


version control with RCS: properties

• working copy vs. repository

• the repository (file,v) holds versions of the working copy, but is not a working copy itself

• no automatic “tracking” of changes in working copies; the user is trusted to check versions in and out as appropriate

• this can lead to conflictsif multiple working copies are edited


limitations of RCS; CVS

• only works on single files• single host: ci / co work on “local” file system

=> CVS (written in 1986 on top of RCS) =>

• RCS on a whole directory tree of files at once• many extra features• repositories can be remote (client/server)• nice GUI clients and repository browsers available

http://groups.google.com/groups?selm=122%40mirror.UUCP&rnum=280

http://www.tortoisecvs.org/

http://ali.as/devel/cvsmonitor/cvs.html


demo 4: CVS for private use

cd ~/bin; cvs log

main CVS commands:• cvs ci file # check current version of file in to $CVSROOT

• cvs co file # check latest version of file out from $CVSROOT

cvs up file # id., if a copy is already available

• cvs add file # put a file under version control in $CVSROOT

• cvs diff file # compare current copy of file with latest in $CVSROOT

file can be a whole directory tree, $CVSROOT can be remote


demo 4 (continued)

cd /tmpcvs –d /home/rp/cvs co scriptscd scriptsrightperl bin/*cvs diff

# on a different host:cd /tmpcvs –d :ext:[email protected]:/home/rp co scripts # via ssh!

http://www.win.tue.nl/~rp/util/rightperl


demo 5: the Tortoise CVS client

a (free) GUI CVS client for Windows

easier to use than the command line,but everything works the same way:

• right-click to get the initial menu, select CVS Checkout ...• select the repository and communication method,• inside the resulting directory you can CVS update and check in

http://www.tortoisecvs.org/


demo 6: CVS for collaboration

co-authoring papers:• one author hosts the CVS repository• gives other author(s) read/write access to it

software development projects:(demo) petriweb.org:• website, software & docs in CVS• checked out automatically (using a CVSROOT/ feature)

http://cvs.horde.org/cvs.php/CVSROOT/?Horde=77847c61a057a9369e12aecf431e2dcd

http://cvs.horde.org/cvs.php/CVSROOT/?Horde=77847c61a057a9369e12aecf431e2dcd


authentication for remote CVS servers

• with the :pserver: protocol:- the CVS server runs as one OS user- user accounts are managed in the CVS server- good for read-only access; too insecure for read-write access

• with :ext: (ssh):- with one CVS server user, slightly better than pserver- with arbitrary repositories for arbitrary groups of people, it requires a lot of account administration (SourceForge: every user can get a Unix account by registering)


demo 7: public CVS

SourceForge ( http://sf.net/ ): over 70,000 CVS repositories (pick one for a demo); mostly software development.

Most of the world’s CVS repositories are elsewhere.


the power of CVS

CVS allows to set up a single repositoryfor all files in a project, with full version control.• you always know where your “good” versions are

and how they are related• multi-user• Internet wide• (largely) platform independent

(on MS Windows you can feel the Unix legacy)


CVS: properties

• working copy vs. repository

• the repository holds versions of the working copy, but is not a working copy itself

• no automatic “tracking” of changes; every user must check in and check out regularly;this can lead to conflictsif multiple working copies are edited


CVS administrative files

In the working copy:• every directory has a subdirectory CVS/

with files used by CVS• the file .cvsignore can be used to tell CVS to ignore files

in the working copy that must not be in the repository

In the repository:• the CVSROOT/ directory contains many files with interesting

configurable settings


CVS caveats

• cvs add only prepares to add files, you need to confirm with cvs ci, and on a directory follow that again with cvs up

• files can be explicitly marked as binary (see the manual) • cvs can cope with the difference between Unix and Windows,

but if files seem corrupted, check the CVS client settings• If you have many conflicts (a working copy has been edited

while a new repository version was added from another source) you need to talk to people, not to CVS.


advanced CVS commands

creating a repository: cvs init, cvs import

branching:• cvs tag file # label current version of file in $CVSROOT

• cvs rtag # label current versions in $CVSROOT

this can be used to create branches, forks of the code• cvs merge args # join two branches together (equiv. of patch)

• cvs edit, cvs editors, cvs watch, etc.:for change notification


CVS: strong points

• entirely free: no cost, no licensing• everybody and their dog uses it: high reliability,

good support via Google• simple: config files are plaintext, the protocol is simple,

source code is free, so it’s very transparent• extensible: it’s easy to wrap stuff around CVS

at client side and server side (e.g. automatic checkout for petriweb.org: CVSROOT/loginfo calls this script)


CVS: weak points

• overly simple: it works on whole directory trees, but- adding/removing files and dirs is confusing- renaming files isn’t supported (except remove + add)- committing multiple files isn’t atomic- no support for hardlinks / symlinks / shortcuts- tagging/branching whole trees is hard to do

• the use of diffs:- performance on binary files is terrible- performance decreases with the number of commits


when to use CVS

CVS is good when• you have a collection of (mostly) text files• you change them or plan to change them regularly

(at least your copies of them)• you and/or others access them from various locations• you want to explicitly record and recall “good”

versions of the files


CVS only offers version control!

It does not offer:• a website for your project• a meeting place / q&a facility for users/authors• problem report / task scheduling facilitiesetc. etc.See again SourceForge for a survey of other facilities

required to support a project.


alternatives to CVS

• no version control:only if you’re sure you’ll only ever need the latest version

• SCCS (standard on Sun Solaris): not popular enough• Subversion and others want to be CVS-like systems that fix

its worst problems. I haven’t tried them.• Microsoft Visual SourceSafe. I haven’t tried it.• more?


CVS vs. filesystem backups/copies

a filesystem copy / backup to another disk or tape:• saves everything indiscriminately• may or may not save it in a useable state• has limited memory for older versions

a CVS repository:• makes the user decide when to save what• expects selective use (not too many files or saves)• keeps perfect memory of everything ever saved


where to go next

To learn how to use CVS:• you don’t need to know much more than this• good manuals are on the Web• it takes a few hours to get used to


CVS @ W&I

Is there any need for a departmental CVS server• for 1-user projects? (I don’t think so)• for collaborations within the dept.? (?)• for collaborations with others? (useful, but I don’t see how to set it up)• as a public server for material? (?)• ?

Other kinds of CVS support? (Training?)

Documents

versiebeheer op bestanden met Subversion