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bitbake: user-manual-fetching.xml: Re-write of the Fetching chapter. 

Based on a Richard Purdie re-write.

(Bitbake rev: fad9a6258f8c04bbe0168e46898dd27b86c39ee0)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark 2014-02-18 17:43:15 -06:00 committed by Richard Purdie
parent cd0c0673dc
commit 9b3e31e5e1
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bitbake/doc/user-manual/user-manual-fetching.xml
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@ -5,57 +5,112 @@
<title>File Download Support</title>
<para>
BitBake's <filename>fetch</filename> and
<filename>fetch2</filename> modules support downloading
files.
This chapter provides an overview of the fetching process
and also presents sections on each of the fetchers BitBake
supports.
<note>
The original <filename>fetch</filename> code, for all
practical purposes, has been replaced by
<filename>fetch2</filename> code.
Consequently, the information in this chapter does not
apply to <filename>fetch</filename>.
</note>
BitBake's fetch module is a standalone piece of library code
that deals with the intricacies of downloading source code
and files from remote systems.
Fetching source code is one of the corner stones of building software.
As such, this module forms an important part of BitBake.
</para>
<section id='file-download-overview'>
<title>Overview</title>
<para>
The current fetch module is called "fetch2" and refers to the
fact that it is the second major version of the API.
The original version is obsolete and removed from the codebase.
Thus, in all cases, "fetch" refers to "fetch2" in this
manual.
</para>
<section id='the-download-fetch'>
<title>The Download (Fetch)</title>
<para>
When BitBake starts to execute, the very first thing
it does is to fetch the source files needed.
This section overviews the process.
BitBake takes several steps when fetching source code or files.
The fetcher codebase deals with two distinct processes in order:
obtaining the files from somewhere (cached or otherwise)
and then unpacking those files into a specific location and
perhaps in a specific way.
Getting and unpacking the files is often optionally followed
by patching.
Patching, however, is not covered by the fetch.
</para>
<para>
When BitBake goes looking for source files, it follows a search
order:
<orderedlist>
The code to execute the first part of this process, a fetch,
looks something like the following:
<literallayout class='monospaced'>
src_uri = (d.getVar('SRC_URI', True) or "").split()
fetcher = bb.fetch2.Fetch(src_uri, d)
fetcher.download()
</literallayout>
This code sets up an instance of the fetch module.
The instance uses a space-separated list of URLs from the
<link linkend='var-SRC_URI'><filename>SRC_URI</filename></link>
variable and then calls the <filename>download</filename>
method to download the files.
</para>
<para>
The instance of the fetch module is usually followed by:
<literallayout class='monospaced'>
rootdir = l.getVar('WORKDIR', True)
fetcher.unpack(rootdir)
</literallayout>
This code unpacks the downloaded files to the
specified by <filename>WORKDIR</filename>.
<note>
For convenience, the naming in these examples matches
the variables used by OpenEmbedded.
</note>
The <filename>SRC_URI</filename> and <filename>WORKDIR</filename>
variables are not coded into the fetcher.
They variables can (and are) called with different variable names.
In OpenEmbedded for example, the shared state (sstate) code uses
the fetch module to fetch the sstate files.
</para>
<para>
When the <filename>download()</filename> method is called,
BitBake tries to fulfill the URLs by looking for source files
in a specific search order:
<itemizedlist>
<listitem><para><emphasis>Pre-mirror Sites:</emphasis>
BitBake first uses pre-mirrors to try and find source
files.
BitBake first uses pre-mirrors to try and find source files.
These locations are defined using the
<link linkend='var-PREMIRRORS'><filename>PREMIRRORS</filename></link>
variable.
</para></listitem>
<listitem><para><emphasis>Source URI:</emphasis>
If pre-mirrors fail, BitBake uses
<link linkend='var-SRC_URI'><filename>SRC_URI</filename></link>.
If pre-mirrors fail, BitBake uses the original URL (e.g from
<filename>SRC_URI</filename>).
</para></listitem>
<listitem><para><emphasis>Mirror Sites:</emphasis>
If fetch failures occur using <filename>SRC_URI</filename>,
BitBake next uses mirror location as defined by the
If fetch failures occur, BitBake next uses mirror location as
defined by the
<link linkend='var-MIRRORS'><filename>MIRRORS</filename></link>
variable.
</para></listitem>
</orderedlist>
</itemizedlist>
</para>
<para>
For each URL passed to the fetcher, the fetcher
calls the submodule that handles that particular URL type.
This behavior can be the source of some confusion when you
are providing URLs for the <filename>SRC_URI</filename>
variable.
Consider the following two URLs:
<literallayout class='monospaced'>
http://git.yoctoproject.org/git/poky;protocol=git
git://git.yoctoproject.org/git/poky;protocol=http
</literallayout>
In the former case, the URL is passed to the
<filename>wget</filename> fetcher, which does not
understand "git".
Therefore, the latter case is the correct form since the
Git fetcher does know how to use HTTP as a transport.
</para>
<para>
Because cross-URLs are supported, it is possible to mirror
a Git repository on an HTTP server as a tarball.
Here are some examples that show commonly used mirror
definitions:
<literallayout class='monospaced'>
@ -74,19 +129,29 @@
http://.*/.* http://somemirror.org/sources/ \n \
https://.*/.* http://somemirror.org/sources/ \n"
</literallayout>
It is useful to note that BitBake supports
cross-URLs.
It is possible to mirror a Git repository on an HTTP
server as a tarball.
This is what the <filename>git://</filename> mapping in
the previous example does.
</para>
<para>
Any source files that are not local (i.e. downloaded from
the Internet) are placed into the download directory,
which is specified by
<link linkend='var-DL_DIR'><filename>DL_DIR</filename></link>.
Since network accesses are slow, Bitbake maintains a
cache of files downloaded from the network.
Any source files that are not local (i.e.
downloaded from the Internet) are placed into the download
directory, which is specified by the
<link linkend='var-DL_DIR'><filename>DL_DIR</filename></link>
variable.
</para>
<para>
File integrity is of key importance for reproducing builds.
For non-local archive downloads, the fetcher code can verify
sha256 and md5 checksums to ensure
the archives have been downloaded correctly.
sha256 and md5 checksums to ensure the archives have been
downloaded correctly.
You can specify these checksums by using the
<filename>SRC_URI</filename> variable with the appropriate
varflags as follows:
@ -97,18 +162,87 @@
You can also specify the checksums as parameters on the
<filename>SRC_URI</filename> as shown below:
<literallayout class='monospaced'>
SRC_URI="http://example.com/foobar.tar.bz2;md5sum=4a8e0f237e961fd7785d19d07fdb994d"
SRC_URI = "http://example.com/foobar.tar.bz2;md5sum=4a8e0f237e961fd7785d19d07f
db994d"
</literallayout>
If multiple URIs exist, you can specify the checksums either
directly as in the previous example, or you can name the URLs.
The following syntax shows how you name the URIs:
<literallayout class='monospaced'>
SRC_URI = "http://example.com/foobar.tar.bz2;name=foo"
SRC_URI[foo.md5sum] = 4a8e0f237e961fd7785d19d07fdb994d
</literallayout>
After a file has been downloaded and has had its checksum checked,
a ".done" stamp is placed in <filename>DL_DIR</filename>.
BitBake uses this stamp during subsequent builds to avoid
downloading or comparing a checksum for the file again.
<note>
It is assumed that local storage is safe from data corruption.
If this were not the case, there would be bigger issues to worry about.
</note>
</para>
<para>
If
<link linkend='var-BB_STRICT_CHECKSUM'><filename>BB_STRICT_CHECKSUM</filename></link>
is set, any download without a checksum triggers an error message.
In cases where multiple files are listed using
<filename>SRC_URI</filename>, the name parameter is used
assign names to the URLs and these are then specified
in the checksums using the following form:
<literallayout class='monospaced'>
SRC_URI[name.sha256sum]
</literallayout>
is set, any download without a checksum triggers an
error message.
The
<link linkend='var-BB_NO_NETWORK'><filename>BB_NO_NETWORK</filename></link>
variable can be used to make any attempted network access a fatal
error, which is useful for checking that mirrors are complete
as well as other things.
</para>
</section>
<section id='bb-the-unpack'>
<title>The Unpack</title>
<para>
The unpack process usually immediately follows the download.
For all URLs except Git URLs, BitBake uses the common
<filename>unpack</filename> method.
</para>
<para>
A number of parameters exist that you can specify within the
URL to govern the behavior of the unpack stage:
<itemizedlist>
<listitem><para><emphasis>unpack:</emphasis>
Controls whether the URL components are unpacked.
If set to "1", which is the default, the components
are unpacked.
If set to "0", the unpack stage leaves the file alone.
This parameter is useful when you want an archive to be
copied in and not be unpacked.
</para></listitem>
<listitem><para><emphasis>dos:</emphasis>
Applies to <filename>.zip</filename> and
<filename>.jar</filename> files and specifies whether to
use DOS line ending conversion on text files.
</para></listitem>
<listitem><para><emphasis>basepath:</emphasis>
Instructs the unpack stage to strip the specified
directories from the source path when unpacking.
</para></listitem>
<listitem><para><emphasis>subdir:</emphasis>
Unpacks the specific URL to the specified subdirectory
within the root directory.
</para></listitem>
</itemizedlist>
The unpack call automatically decompresses and extracts files
with ".Z", ".z", ".gz", ".xz", ".zip", ".jar", ".ipk", ".rpm".
".srpm", ".deb" and ".bz2" extensions as well as various combinations
of tarball extensions.
</para>
<para>
As mentioned, the Git fetcher has its own unpack method that
is optimized to work with Git trees.
Basically, this method works by cloning the tree into the final
directory.
The process is completed using references so that there is
only one central copy of the Git metadata needed.
</para>
</section>
@ -116,47 +250,45 @@
<title>Fetchers</title>
<para>
As mentioned in the previous section, the
<filename>SRC_URI</filename> is normally used to
tell BitBake which files to fetch.
And, the fetcher BitBake uses depends on the how
<filename>SRC_URI</filename> is set.
</para>
<para>
These next few sections describe the available fetchers and
their options.
Each fetcher honors a set of variables URI parameters,
which are separated by semi-colon characters and consist
of a key and a value.
The semantics of the variables and parameters are
defined by the fetcher.
BitBake tries to have consistent semantics between the
different fetchers.
As mentioned earlier, the URL prefix determines which
fetcher submodule BitBake uses.
Each submodule can support different URL parameters,
which are described in the following sections.
</para>
<section id='local-file-fetcher'>
<title>Local file fetcher</title>
<title>Local file fetcher (<filename>file://</filename>)</title>
<para>
The URN for the local file fetcher is file.
</para>
<para>
The filename can be either absolute or relative.
If the filename is relative,
This submodule handles URLs that begin with
<filename>file://</filename>.
The filename you specify with in the URL can
either be an absolute or relative path to a file.
If the filename is relative, the contents of the
<link linkend='var-FILESPATH'><filename>FILESPATH</filename></link>
is used.
variable is used in the same way
<filename>PATH</filename> is used to find executables.
Failing that,
<link linkend='var-FILESDIR'><filename>FILESDIR</filename></link>
is used to find the appropriate relative file.
<note>
<filename>FILESDIR</filename> is deprecated and can
be replaced with <filename>FILESPATH</filename>.
Because <filename>FILESDIR</filename> is likely to be
removed, you should not use this variable in any new code.
</note>
If the file cannot be found, it is assumed that it is available in
<link linkend='var-DL_DIR'><filename>DL_DIR</filename></link>
by the time the <filename>download()</filename> method is called.
</para>
<para>
The metadata usually extend these variables to include
variations of the values in
<link linkend='var-OVERRIDES'><filename>OVERRIDES</filename></link>.
Single files and complete directories can be specified.
If you specify a directory, the entire directory is
unpacked.
</para>
<para>
Here are some example URLs:
<literallayout class='monospaced'>
SRC_URI = "file://relativefile.patch"
SRC_URI = "file://relativefile.patch;this=ignored"
@ -166,36 +298,53 @@
</section>
<section id='cvs-fetcher'>
<title>CVS fetcher</title>
<title>CVS fetcher (<filename>(cvs://</filename>)</title>
<para>
The URN for the CVS fetcher is cvs.
</para>
<para>
This fetcher honors the variables <filename>CVSDIR</filename>,
<filename>SRCDATE</filename>, <filename>FETCHCOMMAND_cvs</filename>,
<filename>UPDATECOMMAND_cvs</filename>.
The
<link linkend='var-DL_DIR'><filename>DL_DIR</filename></link>
variable specifies where a
temporary checkout is saved.
The
<link linkend='var-SRCDATE'><filename>SRCDATE</filename></link>
variable specifies which date to
use when doing the fetching.
The special value of "now" causes the checkout to be
updated on every build.
The <filename>FETCHCOMMAND</filename> and
<filename>UPDATECOMMAND</filename> variables specify the executables
to use for the CVS checkout or update.
This submodule handles checking out files from the
CVS version control system.
You can configure it using a number of different variables:
<itemizedlist>
<listitem><para><emphasis><filename>FETCHCMD_cvs</filename>:</emphasis>
The name of the executable to use when running
the <filename>cvs</filename> command.
This name is usually "cvs".
</para></listitem>
<listitem><para><emphasis><filename>SRCDATE</filename>:</emphasis>
The date to use when fetching the CVS source code.
A special value of "now" causes the checkout to
be updated on every build.
</para></listitem>
<listitem><para><emphasis><filename>CVSDIR</filename>:</emphasis>
Specifies where a temporary checkout is saved.
The location is often <filename>DL_DIR/cvs</filename>.
</para></listitem>
<listitem><para><emphasis><filename>CVS_PROXY_HOST</filename>:</emphasis>
The name to use as a "proxy=" parameter to the
<filename>cvs</filename> command.
</para></listitem>
<listitem><para><emphasis><filename>CVS_PROXY_PORT</filename>:</emphasis>
The port number to use as a "proxyport=" parameter to
the <filename>cvs</filename> command.
</para></listitem>
</itemizedlist>
As well as the standard username and password URL syntax,
you can also configure the fetcher with various URL parameters:
</para>
<para>
The supported parameters are as follows:
<itemizedlist>
<listitem><para><emphasis>"method":</emphasis>
The protocol over which to communicate with the cvs server.
By default, this protocol is "pserver".
If "method" is set to "ext", BitBake examines the
"rsh" parameter and sets <filename>CVS_RSH</filename>.
You can use "dir" for local directories.
</para></listitem>
<listitem><para><emphasis>"module":</emphasis>
Specifies the module to check out.
You must supply this parameter.
</para></listitem>
<listitem><para><emphasis>"tag":</emphasis>
Describes which CVS TAG should be used for
@ -210,23 +359,36 @@
The special value of "now" causes the checkout to be
updated on every build.
</para></listitem>
<listitem><para><emphasis>"method":</emphasis>
By default <filename>pserver</filename>.
If "method" is set to "ext", BitBake examines the "rsh"
parameter and sets <filename>CVS_RSH</filename>.
</para></listitem>
<listitem><para><emphasis>"localdir":</emphasis>
Used to checkout force into a special
Used to rename the module.
Effectively, you are renaming the output directory
to which the module is unpacked.
You are forcing the module into a special
directory relative to <filename>CVSDIR</filename>.
</para></listitem>
<listitem><para><emphasis>"rsh"</emphasis>
Used in conjunction with the "method" parameter.
</para></listitem>
<listitem><para><emphasis>"scmdata":</emphasis>
I need a description for this.
Causes the CVS metadata to be maintained in the tarball
the fetcher creates when set to "keep".
The tarball is expanded into the work directory.
By default, the CVS metadata is removed.
</para></listitem>
<listitem><para><emphasis>"fullpath":</emphasis>
Controls whether the resulting checkout is at the
module level, which is the default, or is at deeper
paths.
</para></listitem>
<listitem><para><emphasis>"norecurse":</emphasis>
Causes the fetcher to only checkout the specified
directory with no recurse into any subdirectories.
</para></listitem>
<listitem><para><emphasis>"port":</emphasis>
The port to which the CVS server connects.
</para></listitem>
</itemizedlist>
Following are two examples using cvs:
Some example URLs are as follows:
<literallayout class='monospaced'>
SRC_URI = "cvs://CVSROOT;module=mymodule;tag=some-version;method=ext"
SRC_URI = "cvs://CVSROOT;module=mymodule;date=20060126;localdir=usethat"
@ -235,19 +397,27 @@
</section>
<section id='http-ftp-fetcher'>
<title>HTTP/FTP fetcher</title>
<title>HTTP/FTP wget fetcher (<filename>http://</filename>, <filename>ftp://</filename>, <filename>https://</filename>)</title>
<para>
The URNs for the HTTP/FTP fetcher are http, https, and ftp.
This fetcher obtains files from web and FTP servers.
Internally, the fetcher uses the wget utility.
</para>
<para>
This fetcher honors the variables
<filename>FETCHCOMMAND_wget</filename>.
The <filename>FETCHCOMMAND</filename> variable
contains the command used for fetching.
“${URI}” and “${FILES}” are replaced by the URI and
the base name of the file to be fetched.
The executable and parameters used are specified by the
<filename>FETCHCMD_wget</filename> variable, which defaults
to a sensible values.
The fetcher supports a parameter "downloadfilename" that
allows the name of the downloaded file to be specified.
Specifying the name of the downloaded file is useful
for avoiding collisions in
<link linkend='var-DL_DIR'><filename>DL_DIR</filename></link>
when dealing with multiple files that have the same name.
</para>
<para>
Some example URLs are as follows:
<literallayout class='monospaced'>
SRC_URI = "http://oe.handhelds.org/not_there.aac"
SRC_URI = "ftp://oe.handhelds.org/not_there_as_well.aac"
@ -257,36 +427,46 @@
</section>
<section id='svn-fetcher'>
<title>SVN Fetcher</title>
<title>Subversion (SVN) Fetcher (<filename>svn://</filename>)</title>
<para>
The URN for the SVN fetcher is svn.
</para>
<para>
This fetcher honors the variables
<filename>FETCHCOMMAND_svn</filename>,
<filename>SVNDIR</filename>,
and
<link linkend='var-SRCREV'><filename>SRCREV</filename></link>.
The <filename>FETCHCOMMAND</filename> variable contains the
<filename>subversion</filename> command.
The <filename>SRCREV</filename> variable specifies which revision
to use when doing the fetching.
This fetcher submodule fetches code from the
Subversion source control system.
The executable used is specified by
<filename>FETCHCMD_svn</filename>, which defaults
to "svn".
The fetcher's temporary working directory is set
by <filename>SVNDIR</filename>, which is usually
<filename>DL_DIR/svn</filename>.
</para>
<para>
The supported parameters are as follows:
<itemizedlist>
<listitem><para><emphasis>"proto":</emphasis>
The Subversion protocol.
<listitem><para><emphasis>"module":</emphasis>
The name of the svn module to checkout.
You must provide this parameter.
You can think of this parameter as the top-level
directory of the repository data you want.
</para></listitem>
<listitem><para><emphasis>"protocol":</emphasis>
The protocol to use, which defaults to "svn".
Other options are "svn+ssh" and "rsh".
For "rsh", the "rsh" parameter is also used.
</para></listitem>
<listitem><para><emphasis>"rev":</emphasis>
The Subversion revision.
The revision of the source code to checkout.
</para></listitem>
<listitem><para><emphasis>"date":</emphasis>
The date of the source code to checkout.
Specific revisions are generally much safer to checkout
rather than by date as they do not involve timezones
(e.g. they are much more deterministic).
</para></listitem>
<listitem><para><emphasis>"scmdata":</emphasis>
Set to "keep" causes the “.svn” directories
to be available during compile-time.
Causes the “.svn” directories to be available during
compile-time when set to "keep".
By default, these directories are removed.
</para></listitem>
</itemizedlist>
Following are two examples using svn:
@ -298,40 +478,150 @@
</section>
<section id='git-fetcher'>
<title>GIT Fetcher</title>
<title>GIT Fetcher (<filename>git://</filename>)</title>
<para>
The URN for the Git Fetcher is git.
This fetcher submodule fetches code from the Git
source control system.
The fetcher works by creating a bare clone of the
remote into <filename>GITDIR</filename>, which is
usually <filename>DL_DIR/git</filename>.
This bare clone is then cloned into the work directory during the
unpack stage when a specific tree is checked out.
This is done using alternates and by reference to
minimize the amount of duplicate data on the disk and
make the unpack process fast.
The executable used can be set with
<filename>FETCHCMD_git</filename>.
</para>
<para>
The variable <filename>GITDIR</filename> is used as the
base directory in which the Git tree is cloned.
</para>
<para>
The supported parameters are as follows:
This fetcher supports the following parameters:
<itemizedlist>
<listitem><para><emphasis>"tag":</emphasis>
The Git tag.
The default is "master".
</para></listitem>
<listitem><para><emphasis>"protocol":</emphasis>
The Git protocol.
The protocol used to fetch the files.
The default is "git" when a hostname is set.
If a hostname is not set, the Git protocol is "file".
You can also use "http", "https", "ssh" and "rsync".
</para></listitem>
<listitem><para><emphasis>"scmdata":</emphasis>
When set to “keep”, the “.git” directory is available
during compile-time.
<listitem><para><emphasis>"nocheckout":</emphasis>
Tells the fetcher to not checkout source code when
unpacking when set to "1".
Set this option for the URL where there is a custom
routine to checkout code.
The default is "0".
</para></listitem>
<listitem><para><emphasis>"rebaseable":</emphasis>
Indicates that the upstream Git repository can be rebased.
You should set this parameter to "1" if
revisions can become detached from branches.
In this case, the source mirror tarball is done per
revision, which has a loss of efficiency.
Rebasing the upstream Git repository could cause the
current revision to disappear from the upstream repository.
This option reminds the fetcher to preserve the local cache
carefully for future use.
The default value for this parameter is "0".
</para></listitem>
<listitem><para><emphasis>"nobranch":</emphasis>
Tells the fetcher to not check the SHA validation
for the branch when set to "1".
The default is "0".
Set this option for the recipe that refers to
the commit that is valid for a tag instead of
the branch.
</para></listitem>
<listitem><para><emphasis>"bareclone":</emphasis>
Tells the fetcher to clone a bare clone into the
destination directory without checking out a working tree.
Only the raw Git metadata is provided.
This parameter implies the "nocheckout" parameter as well.
</para></listitem>
<listitem><para><emphasis>"branch":</emphasis>
The branch(es) of the Git tree to clone.
If unset, this is assumed to be "master".
The number of branch parameters much match the number of
name parameters.
</para></listitem>
<listitem><para><emphasis>"rev":</emphasis>
The revision to use for the checkout.
The default is "master".
</para></listitem>
<listitem><para><emphasis>"tag":</emphasis>
Specifies a tag to use for the checkout.
To correctly resolve tags, BitBake must access the
network.
For that reason, tags are often not used.
As far as Git is concerned, the "tag" parameter behaves
effectively the same as the "revision" parameter.
</para></listitem>
<listitem><para><emphasis>"subpath":</emphasis>
Limits the checkout to a specific subpath of the tree.
By default, the whole tree is checked out.
</para></listitem>
<listitem><para><emphasis>"destsuffix":</emphasis>
The name of the path in which to place the checkout.
By default, the path is <filename>git/</filename>.
</para></listitem>
</itemizedlist>
Following are two examples using git:
Here are some example URLs:
<literallayout class='monospaced'>
SRC_URI = "git://git.oe.handhelds.org/git/vip.git;tag=version-1"
SRC_URI = "git://git.oe.handhelds.org/git/vip.git;protocol=http"
</literallayout>
</para>
</section>
<section id='other-fetchers'>
<title>Other Fetchers</title>
<para>
Fetch submodules also exist for the following:
<itemizedlist>
<listitem><para>
Bazzar (<filename>bzr://</filename>)
</para></listitem>
<listitem><para>
Perforce (<filename>p4://</filename>)
</para></listitem>
<listitem><para>
SVK
</para></listitem>
<listitem><para>
Git Submodules (<filename>gitsm://</filename>)
</para></listitem>
<listitem><para>
Trees using Git Annex (<filename>gitannex://</filename>)
</para></listitem>
<listitem><para>
Secure FTP (<filename>sftp://</filename>)
</para></listitem>
<listitem><para>
Secure Shell (<filename>ssh://</filename>)
</para></listitem>
<listitem><para>
Repo (<filename>repo://</filename>)
</para></listitem>
<listitem><para>
OSC (<filename>osc://</filename>)
</para></listitem>
<listitem><para>
Mercurial (<filename>hg://</filename>)
</para></listitem>
</itemizedlist>
No documentation currently exists for these lesser used
fetcher submodules.
However, you might find the code helpful and readable.
</para>
</section>
</section>
<section id='auto-revisions'>
<title>Auto Revisions</title>
<para>
We need to document <filename>AUTOREV</filename> and
<filename>SRCREV_FORMAT</filename> here.
</para>
</section>
</chapter>