Integrated version control with Fossil SCM

Integrated version control with Fossil SCM Tech Talk 2009-12-01 Arne Bachmann

Overview
Web address
www.fossil-scm.org
Author
Dr. D.R. Hipp - Author of
License
GPL v2
Motto
No information gets ever lost

Fossil principles
In Fossil, a revision is called check-in
Every file, branch and check-in is an immutable artifact with an artifact identifier (AID), which is a SHA-1 hash
E.g. f3859e6842b68349fe52128767e64c4329e4a4
But it suffices to use prefixes (e.g. f385 , usually 8 letters)
Additionally you can tag (name) branches for easier access

Fossil principles
Fossil is leightweight
Compilation is a matter of seconds, including SQLite code
One executable 787kB including self-tests & documentation
No dependency whatsoever on external libs or tools: gzip, diff, rsync, Python, Perl, Tcl, Java, Apache, Dbs, patch, …
Fossil is self-hosted
The website fossil-scm.org runs on fossil as CGI

Usability: Command line interface
Comfortable command-line interface
Prefixes suffices for commands & AIDs
fossil commit -> fossil com
fossil rebuild -> fossil reb
Fossil reconstruct -> fossil rec
fossil co = checkout -> fossil che
Symbolic names for check-ins
Simple tags on a check-in, starting with sym-
No tab-completion integrated, since there's no fossil shell

Usability: Web interface
Fossil runs as a web server, provides a comfortable interface
fossil ui or
fossil server

Usability: Desktop interface
… not yet available

Features
Distributed version control system
Similar to Mercurial & Bazaar (Python), Git (C), BitKeeper
Very fast (pure C code)
Data-efficient (stores and syncs (binary) deltas, zlib'ed)
Fossil is safe:
SQLite manages all data + BLOBs, transactional
Extensive self-testing upon each action (zlib-(de)compress), checksumming for every artifact and every action

Features
Very simple and persistent data structures for deltas, tables and file formats
No need to dump data off a repository, because each repository is always exactly one file
Migration very easy: close , <move> , open
No need to import dumped data, because upgrading a repository to a younger fossil executable is that easy:
fossil all rebuild

Fossil: Main building blocks (SCM)
Fossil is a VCS, but additionally each repository contains
A ticket system (bugtracker)
History independent of check-in history
A simple Wiki with edit-inside-the-browser
Each wiki page has its own history, independent of check-ins
Pages can theoretically be branched and merged
But currently no UI or API for that
Embedded documentation linked with check-ins
Reachable by <server>/ doc /<dir>/<page>.wiki
CSS can be changed via admin options from the UI

Tags
… can be attached to any leaf
Can have a value (= property), but mostly need none
Can be symbolic (starting with sym- )
Are passed on to descendants
Unless cancelled ( fossil tag cancel <name> )
Unless merging with another branch
There are two default tags:
branch=trunk represents the current branch
sym-trunk (= NULL) symbolic name of branch
After branching
sym-trunk : cancelled

Branching
Forking vs. Branching?
Fork defined as an "accidental" split of the check-in tree
Branch defined as deliberate
e.g. a test branch is often merged into the main development branch, point of branch = branch point
Merging
No integrated conflict editor (but the usual in-file notation)

Configuration
Local configuration state
Not shared when pushing, pulling, (auto) syncing
Contains settings regarding
Used tools
commit message editor
Web browser
(Graphical) diff tool
Encryption
Proxy
Sync options
Behaviour (autosync …)

Configuration
fossil help settings
Shows integrated help

Server mode
Fossil allows to quickly sync with other developers' repositories
fossil server or fossil ui (opens local web browser)
fossil push offers changes to remote fossil instance
fossil pull loads changes from a remote fossil instance
But doesn't change current check-in state (use update)
fossil sync pulls and pushes
As above
Autosync mode offers operation similar to working with a central subversion repository -> fossil is very flexible

Server mode
Comprehensive web interface allows easy administration
Of users and user rights (+ inherited group rights)
Settings
Appearance
Logs
Statistics
CGI integration
Serving multiple repositories

Additional advantages of Fossil
User rights management
Uses current login name under Windows/Linux
Separate rights for check-ins and web interface users
Integrated check-in signing
Via PGP/GPG keys or similar
Or use --nosign upon commit and branch
Robust and reliable
Several years of experience in multi-project, multi-GB source trees with thousands of files and check-ins

Drawbacks
Commercial support from a very small company (only 2 persons?)
No graphical Windows client available yet
Especially no conflict editor and explorer integration

Questions? http://www.walle-derfilm.de/

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