Fossil

development of a software project and to record the history
of the project.
There are many such systems in use today.  Fossil strives to
distinguish itself from the others by being extremely simple
to setup and operate.

This document is intended as a quick introduction to the concepts
behind fossil.

<h2>2.0 Composition Of A Project</h2>
<img src="concept1.gif" align="right" hspace="10">

A software project normally consists of a "source tree".
A source tree is a hierarchy of files that are used to generate
the end product.  The source tree changes over time as the
software grows and expands and as features are added and bugs
are fixed.  A snapshot of the source tree at any point in time
is called a "version" or "revision" or a "baseline" of the product.
In fossil, we use the name "check-in".

A "repository" is a database that contains copies of all historical
check-ins for a project.  Check-ins are normally stored in the
repository in a highly space-efficient compressed format (delta encoding).
But that is an implementation detail that you the user need not worry over.
Think of the repository as a safe place where all your old check-ins are
securely stored away and available for retrieval whenever you need
them.

A repository in fossil is a single file on your disk.  This file
might be rather large (dozens or hundreds of megabytes for a large
or long running project) but it is nevertheless just a file.  You
can move it around, rename it, write it out to a memory stick, or
do anything else you normally do with files.

Each source tree that is controlled by fossil is associated with
a single repository on the local disk drive.  You can tie two or more
source trees to a single repository if you want (though one
tree per repository is the most common configuration.)  So a
single repository can be associated with many source trees, but
each source tree is associated with only one repository.

Fossil source trees may not overlap.  A fossil source tree is identified
by a file named "_FOSSIL_" (or ".fslckout", but this article will always
use the name "_FOSSIL_") in the root directory of the source tree.  Every
file that is a sibling of _FOSSIL_ and every file in every subfolder is
considered potentially a part of the source tree.  The _FOSSIL_ file
contains (among other things) the pathname of the repository with which
the source tree is associated.  On the other hand, the repository has
no record of its source trees.  So you are free to delete a source tree

6089f0b563a9db0a6d90682fe47fd7161ff867c8<br>
59712614a1b3ccfd84078a37fa5b606e28434326<br>
19dbf73078be9779edd6a0156195e610f81c94f9<br>
b4104959a67175f02d6b415480be22a239f1f077<br>
997c9d6ae03ad114b2b57f04e9eeef17dcb82788
</b></blockquote>

When referring to an artifact using fossil, you can use a unique
prefix of the artifact ID that is four characters or longer.  This saves
a lot of typing.  When displaying artifact IDs, fossil will usually only
show the first 10 digits since that is normally enough to uniquely
identify a file.

Changing (or adding or removing) a single byte in a file results
in a completely different artifact ID.  And since the artifact ID is the name of
the artifact, making any change to a file results in a new artifact.
In this way, artifacts are immutable.

Associated with every check-in is a special file called the
[./fileformat.wiki#manifest| "manifest"].  The manifest is a
listing of all other files in
that source tree.  The manifest contains the (complete) artifact ID 
of the file and the name of the file as it appears on disk,
and thus serves as a mapping from artifact ID to disk name.  The artifact ID
of the manifest is the identifier for the entire check-in.  When
you look at a "timeline" of changes in fossil, the ID associated
with each check-in or commit is really just the artifact ID of the
manifest for that check-in.

<p>The manifest file is not normally a real file on disk.  Instead,
the manifest is computed in memory by Fossil whenever it needs it.
However, the "fossil setting manifest on" command will cause the
manifest file to be materialized to disk, if desired.  Both Fossil

<li>A <b>check-in</b> is a set of files arranged
    in a hierarchy.</li>
<li>A <b>repository</b> keeps a record of historical check-ins.</li>
<li>Repositories share their changes using <b>push</b>, <b>pull</b>,
    <b>sync</b>, and <b>clone</b>.</li>
<li>A particular <u>version</u> of a particular file is an <b>artifact</b>
    that is identified by an <b>artifact ID</b>.</li>
<li>Artifacts tracked by fossil are inherently immutable.</li>
<li>Fossil automatically generates a <b>manifest</b> file that identifies
    every artifact in a check-in.</li>
<li>The artifact ID of the manifest is the identifier of the check-in.</li>
</ul>

<h2>3.0 Fossil - The Program</h2>

Fossil is software.  The implementation of fossil is in the form
of a single executable named "fossil" (or "fossil.exe" on Windows).
To install fossil on your system,
all you have to do is obtain a copy of this one executable file (either
by downloading a
<a href="http://www.fossil-scm.org/download.html">pre-compiled version</a>
or [./build.wiki | compiling it yourself]) and then
putting that file somewhere on your PATH.

Fossil is completely self-contained.  It is not necessary to
install any other software in order to use fossil.  You do <u>not</u> need
CVS, gzip, diff, rsync, Python, Perl, Tcl, Java, apache, PostgreSQL, MySQL,
SQLite, patch, or any similar software on your system in order to use
fossil effectively.  You will want to have some kind of text editor
for entering check-in comments.  Fossil will use whatever text editor
is identified by your VISUAL environment variable.  Fossil will also
use GPG to clearsign your manifests if you happen to have it installed,
but fossil will skip that step if GPG missing from your system.
You can optionally set up fossil to use external "diff" programs, 
though fossil has an excellent built-in "diff" algorithm that works
fine for most people.  If you happen to have Tcl/Tk installed on your
system, Fossil will use it to generate a graphical "diff" display when
you use the --tk option to the "diff" command, but this too is entirely
optional.


To uninstall fossil, simply delete the executable.

To upgrade an older version of fossil to a newer version, just
replace the old executable with the new one.  You might need to 
run "<b>fossil all rebuild</b>" to restructure your repositories after
an upgrade.  Running "all rebuild" never hurts, so when upgrading it
is a good policy to run it even if it is not strictly necessary.

To use fossil, simply type the name of the executable in your
shell, followed by one of the various built-in commands and
arguments appropriate for that command.  For example:

<blockquote><b>
fossil help
</b></blockquote>

In the next section, when we say things like "use the <b>help</b>
command" we mean to use the command name "help" as the first
token after the name of the fossil executable, as shown above.

<a name="workflow"></a>
<h2>4.0 Workflow</h2>

<img src="concept2.gif" align="right" hspace="10">

Fossil has two modes of operation: <i>"autosync"</i> and
<i>"manual-merge"</i>
Autosync mode is reminiscent of CVS or SVN in that it automatically
keeps your changes in synchronization with your co-workers through
the use of a central server.  The manual-merge mode is the standard workflow
for GIT or Mercurial in that your local repository develops
independently of your coworkers and you share and merge your changes manually.
An interesting feature of fossil is that it supports both autosync
and manual-merge work flows.

The default setting for fossil is to be in autosync mode.  You
can change the autosync setting or check the current autosync
setting using commands like:

<blockquote>
<b>fossil setting autosync on<br>
fossil setting autosync off<br>
<b>fossil settings</b>
</blockquote>

By default, fossil runs with autosync mode turned on.  The
authors finds that projects run more smoothly in autosync mode since
autosync helps to prevent pointless forking and merge and helps keeps
all collaborators working on exactly the same code rather than on their
own personal forks of the code.  In the author's view, manual-merge mode
should be reserved for disconnected operation.

<h3>4.1 Autosync Workflow</h3>

to exist in historical check-ins.)  Test your changes.
</li>

<li>
Create a new check-in using the <b>commit</b> command.  You will be prompted
for a check-in comment and also for your GPG key if you have GPG installed.
The commit copies the edits you have made in your local source
tree into your local repository.  After your commit completes, fossil will
automatically <b>push</b> your changes back to the server
you cloned from or whatever server you most recently synced with.
</li>

<li>
When your coworkers make their own changes, you can merge those changes
into your local local source tree using the <b>update</b> command.  

</ol>

<h2>5.0 Setting Up A Fossil Server</h2>

With other configuration management software, setting up a server is
a lot of work and normally takes time, patience, and a lot of system
knowledge.  Fossil is designed to avoid this frustration.  Setting up
a server with fossil is ridiculously easy.  You have four options:</p>

<ol>
<li><p><b>Stand-alone server.</b>
Simply run the [/help?cmd=server|fossil server] or
[/help?cmd=ui|fossil ui] command from the command-line.

<li><p><b>CGI.</b>