<title>Project Documentation</title>

Fossil provides a built-in <a href="wikitheory.wiki">wiki</a>
that can be used to store the
documentation for a project.  This is sufficient for many projects.
If your project is well-served by wiki documentation, then you
need read no further.

But fossil also supports embedding project documentation as
files in the source tree.  There are several potential advantages
to this approach:

  1.  The documentation files are versioned together with the
      source code files so it is always clear what version of
      the documentation goes with a particular release.

  2.  The documentation files can be edited using your favorite
      text editor instead of having to use the web-based wiki
      editor.

  3.  Only people with check-in privileges can modify the documentation.
      (This might be either an advantage or disadvantage, depending
      on the nature of your project.)

We will call documentation that is included as files in the source tree
"embedded documentation".

<h1>1.0 Fossil Support For Embedded Documentation</h1>

The fossil web interface supports embedded documentation using
the "/doc" page.  To access embedded documentation, one points
a web browser to a fossil URL of the following form:

<pre>
<i>&lt;baseurl&gt;</i><big><b>/doc/</b></big><i>&lt;version&gt;</i><big><b>/</b></big><i>&lt;filename&gt;</i>
</pre>

The <i>&lt;baseurl&gt;</i> is the main URL used to access the fossil web server.
For example, the <i>&lt;baseurl&gt;</i> for the fossil project itself is
[https://fossil-scm.org/home].
If you launch the web server using the "[/help?cmd=ui|fossil ui]" command line,
then the <i>&lt;baseurl&gt;</i> is usually
<b>http://localhost:8080/</b>.

The <i>&lt;version&gt;</i> is the
[./checkin_names.wiki|name of a check-in]
that contains the embedded document.  This might be a hash prefix for
the check-in, or it might be the name of a branch or tag, or it might
be a timestamp.  See the prior link
for more possibilities and examples.

The <i id="ckout">&lt;version&gt;</i> can
also be the special identifier "<b>ckout</b>".
The "<b>ckout</b>" keywords means to
pull the documentation file from the local source tree on disk, not
from the any check-in.  The "<b>ckout</b>" keyword
only works when you start your server using the 
"[/help?cmd=server|fossil server]" or "[/help?cmd=ui|fossil ui]"
commands.  The "/doc/ckout" URL is intended to show a preview of
the documentation you are currently editing but have not yet checked in.

The original designed purpose of the "ckout" feature is to allow the
user to preview local changes to documentation before committing the
change.  This is an important facility, since unlike other document
languages like HTML, there is still a lot of variation among rendering
engines for Fossil's markup languages, Markdown and Fossil Wiki.  Your
changes may look fine in your whizzy GUI Markdown editor, but what
actually matters is how <i>Fossil</i> will interpret your Markdown text.
Therefore, you should always preview your edits before committing them.

To help make "ckout" easier to use, the "[/help?cmd=ui|fossil ui]"
command has the "--ckout-alias NAME" option that makes NAME an
alias for "ckout".  If you are editing a collection of documents
that have hardcoded links to one another in the form of
"/doc/trunk/...", for example, you can test your changes by
running "fossil ui --ckout-alias trunk" and all of the links will
point to your uncommitted edits rather than to the latest trunk
check-in.

Finally, the <i>&lt;filename&gt;</i> element of the URL is the
pathname of the documentation file relative to the root of the source
tree.

The mimetype (and thus the rendering) of documentation files is
determined by the file suffix.  Fossil currently understands
[/mimetype_list|many different file suffixes],
including all the popular ones such as ".css", ".gif", ".htm",
".html", ".jpg", ".jpeg", ".png", and ".txt".

Documentation files whose names end in ".wiki" use the
[/wiki_rules | fossil wiki markup] -
a safe subset of HTML together with some wiki rules for paragraph
breaks, lists, and hyperlinks.
Documentation files ending in ".md" or ".markdown" use the
[/md_rules  | Markdown markup language].
Documentation files ending in ".txt" are plain text.
Wiki, markdown, and plain text documentation files
are rendered with the standard fossil header and footer added.
Most other mimetypes are delivered directly to the requesting
web browser without interpretation, additions, or changes.

<h2 id="html">1.1 HTML Rendering With Fossil Headers And Footers</h2>

Files with the mimetype "text/html" (the .html or .htm suffix) are
usually rendered directly to the browser without interpretation.
However, if the file begins with a &lt;div&gt; element like this:

    <b>&lt;div class='fossil-doc' data-title='<i>Title Text</i>'&gt;</b>

Then the standard Fossil header and footer are added to the document
prior to being displayed.  The "class='fossil-doc'" attribute is
required for this to occur.  The "data-title='...'" attribute is
optional, but if it is present the text will become the title displayed
in the Fossil header.  An example of this can be seen in Fossil
Documentation Index www/permutedindex.html:

  *  [/file/www/permutedindex.html?txt|source text for <b>www/permutedindex.html</b>]
  *  [/doc/trunk/www/permutedindex.html|<b>www/permutedindex.html</b> rendered as HTML]

Beware that such HTML files render in the same browser security context
as all other embedded documentation served from Fossil; they are not
fully-independent web pages. One practical consequence of this is that
embedded <tt>&lt;script&gt;</tt> tags will cause a
[https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP | Content
Security Policy] error in your browser with the default CSP as served by
Fossil. See the documentation on [./customskin.md#headfoot | Header and
Footer Processing] and [./defcsp.md | The Default CSP].


<h1>2.0 Server-Side Text Substitution</h1>

Fossil can do a few types of substitution of server-side information
into the embedded document.

<h2>2.1 "$ROOT" In HTML and Markdown Hyperlinks</h2>

Hyperlinks in Markdown and HTML embedded documents can reference 
the root of the Fossil repository using the special text "$ROOT"
at the beginning of a URL. For example, a Markdown hyperlink to
the Markdown formatting rules might be
written in the embedded document like this:

<verbatim>
[Markdown formatting rules]($ROOT/wiki_rules)
</verbatim>

Depending on how the how the Fossil server is configured, that hyperlink
might be renderer like one of the following:

<verbatim>
<a href="/wiki_rules">Wiki formatting rule</a>
<a href="/cgi-bin/fossil/wiki_rules">Wiki formatting rules</a>
</verbatim>

So, in other words, the "$ROOT" text is converted into whatever
the "&lt;baseurl&gt;" is for the document.

This substitution works for HTML and Markdown documents.
It does not work for Wiki embedded documents, since with
Wiki you can just begin a URL with "/" and it automatically knows
to prepend the $ROOT.

<h2>2.2 "$CURRENT" In "/doc/" Hyperlinks</h2>

Similarly, URLs of the form "/doc/$CURRENT/..." have the check-in
hash of the check-in currently being viewed substituted in place of
the "$CURRENT" text.  This feature, in combination with the "$ROOT"
substitution above, allows an absolute path to be used for hyperlinks.

For example, if an embedded document documented wanted to reference
some other document in a separate file named "www/otherdoc.md",
it could use a URL like this:

<verbatim>
[Other Document]($ROOT/doc/$CURRENT/www/otherdoc.md)
</verbatim>

As with "$ROOT", this substitution only works for Markdown and HTML
documents.  For Wiki documents, you would need to use a relative URL.

<h2 id="th1">2.3 TH1 Documents</h2>

Enabling TH1 document support requires the following:

   *  Configure the build with the <code>--with-th1-docs</code> flag.
   *  Enable the <code>th1-docs</code> setting, which is only available
      after building with <code>--with-th1-docs</code>.
   *  Affected files must have a <code>.th1</code> file extension.
   *  The code to run must be embedded in blocks of
      <code>&lt;th1>...&lt;/th1></code>.

Fossil will substitute the value of [./th1.md | TH1 expressions]
within the <code>&lt;th1>...&lt;/th1></code> blocks into
the output HTML.

Since TH1 is a full scripting language, this feature essential grants
the ability to execute code on the server to anyone with check-in
privilege for the project.
This is a security risk that needs to be carefully managed.
The feature is off by default.
Administrators should understand and carefully assess the risks
before enabling the use of TH1 within embedded documentation.


<h1>3.0 Examples</h1>

This file that you are currently reading is an example of
embedded documentation.  The name of this file in the fossil
source tree is "<b>www/embeddeddoc.wiki</b>".
You are perhaps looking at this
file using the URL:

<pre>[https://fossil-scm.org/home/doc/trunk/www/embeddeddoc.wiki]</pre>

The first part of this path, the "[https://fossil-scm.org/home]",
is the base URL.  You might have originally typed:
[https://fossil-scm.org/].  The web server at the fossil-scm.org
site automatically redirects such links by appending "home".  The
"home" file on fossil-scm.org is really a [./server/any/cgi.md|CGI script]
which runs the fossil web service in CGI mode.
The "home" CGI script looks like this:

<pre>
#!/usr/bin/fossil
repository: /fossil/fossil.fossil
</pre>

This is one of the many ways to set up a
<a href="./server/">Fossil server</a>.

The "<b>/trunk/</b>" part of the URL tells fossil to use
the documentation files from the most recent trunk check-in.
If you wanted to see an historical version of this document,
you could substitute the name of a check-in for "<b>/trunk/</b>".
For example, to see the version of this document associated with
check-in [9be1b00392], simply replace the "<b>/trunk/</b>" with
"<b>/9be1b00392/</b>".  You can also substitute the symbolic name
for a particular version or branch.  For example, you might
replace "<b>/trunk/</b>" with "<b>/experimental/</b>" to get the latest
version of this document in the "experimental" branch.  The symbolic name
can also be a date and time string in any of the following formats:</p>

<ul>
<li> <i>YYYY-MM-DD</i>
<li> <i>YYYY-MM-DD<b>T</b>HH:MM</i>
<li> <i>YYYY-MM-DD<b>T</b>HH:MM:SS</i>
</ul>

When the symbolic name is a date and time, fossil shows the version
of the document that was most recently checked in as of the date
and time specified.  So, for example, to see what the fossil website
looked like at the beginning of 2010, enter:

<pre><a href="https://fossil-scm.org/home/doc/2010-01-01/www/index.wiki">https://fossil-scm.org/home/doc/<b>2010-01-01</b>/www/index.wiki
</a></pre>

The file that encodes this document is stored in the fossil source tree under
the name "<b>www/embeddeddoc.wiki</b>" and so that name forms the
last part of the URL for this document.

As I sit writing this documentation file, I am testing my work by
running the "<b>fossil ui</b>" command line and viewing
<b>http://localhost:8080/doc/ckout/www/embeddeddoc.wiki</b> in
Firefox.  I am doing this even though I have not yet checked in
the "<b>www/embeddeddoc.wiki</b>" file for the first time.  Using
the special "<b>ckout</b>" version identifier on the "<b>/doc</b>" page
it is easy to make multiple changes to multiple files and see how they all
look together before committing anything to the repository.
