document http options in new apt-transport-http manpage

We had documentation for the http transport in our "catch-all" apt.conf
manpage, but it seems benefitial to document transports in their own
manpage instead of pushing them all into one.

6 files changed, 158 insertions, 73 deletions

diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index 73d808c64..df88eb809 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -84,6 +84,7 @@ add_docbook(apt-man MANPAGE ALL
         apt_preferences.5.xml
         apt-secure.8.xml
         apt-sortpkgs.1.xml
+        apt-transport-http.1.xml
         sources.list.5.xml
     DEPENDS ${ENTITIES}
     TRANSLATED_ENTITIES ${TRANSLATED_ENTITIES}
diff --git a/doc/apt-transport-http.1.xml b/doc/apt-transport-http.1.xml
new file mode 100644
index 000000000..546e47761
--- /dev/null
+++ b/doc/apt-transport-http.1.xml
@@ -0,0 +1,138 @@
+<?xml version="1.0" encoding="utf-8" standalone="no"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+<!ENTITY % aptent SYSTEM "apt.ent"> %aptent;
+<!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent"> %aptverbatiment;
+<!ENTITY % aptvendor SYSTEM "apt-vendor.ent"> %aptvendor;
+]>
+
+<refentry>
+
+ <refentryinfo>
+   &apt-author.team;
+   &apt-email;
+   &apt-product;
+   <!-- The last update date -->
+   <date>2017-11-22T00:00:00Z</date>
+ </refentryinfo>
+
+ <refmeta>
+   <refentrytitle>apt-transport-http</refentrytitle>
+   <manvolnum>1</manvolnum>
+   <refmiscinfo class="manual">APT</refmiscinfo>
+ </refmeta>
+
+ <!-- Man page title -->
+ <refnamediv>
+    <refname>apt-transport-http</refname>
+    <refpurpose>APT transport for downloading via the Hypertext Transfer Protocol (HTTP)</refpurpose>
+ </refnamediv>
+
+<refsect1><title>Description</title>
+<para>This APT transport allows the use of repositories accessed via the
+Hypertext Transfer Protocol (HTTP). It is available by default and probably the
+most used of all transports. Note that a transport is never called directly by
+a user but used by APT tools based on user configuration.</para>
+<para>HTTP is an unencrypted transport protocol meaning that the
+whole communication with the remote server (or proxy) can be observed by a
+sufficiently capable attacker referred to commonly as man in the middle (MITM).
+Such an attacker can <emphasis>not</emphasis> modify the communication to compromise
+the security of your system through as APTs data security model is independent of the
+chosen transport method. This is explained in detail in &apt-secure;. An overview over
+available transport methods is given in &sources-list;.</para>
+</refsect1>
+
+<refsect1><title>Options</title>
+<para>Various options are available to modify its behaviour which can be set in
+an &apt-conf; file ranging from proxy configuration to workaround for specific
+server insufficiencies.</para>
+
+<refsect2><title>Proxy Configuration</title>
+<para>The environment variable <envar>http_proxy</envar> is supported for system wide configuration.
+Proxies specific to apt can be configured via the option <literal>Acquire::http::Proxy</literal>.
+Proxies which should be used only for certain hosts can be specified via
+<literal>Acquire::http::Proxy::<replaceable>host</replaceable></literal>. Even more finegrained control
+can be achieved via proxy autodetection detailed further below.
+All these options use the URI format <literal><replaceable>scheme</replaceable>://[[<replaceable>user</replaceable>][:<replaceable>pass</replaceable>]@]<replaceable>host</replaceable>[:<replaceable>port</replaceable>]/</literal>.
+Supported URI schemes are <literal>socks5h</literal> (SOCKS5 with remote DNS resolution), <literal>http</literal> and <literal>https</literal>.
+Authentification details can be supplied via &apt-authconf; instead of including it in the URI directly.</para>
+<para>The various APT configuration options support the special value <literal>DIRECT</literal> meaning that
+no proxy should be used. The environment variable <envar>no_proxy</envar> with the same propose is also supported.</para>
+<para>Further more there are three settings provided for cache control with HTTP/1.1 compliant proxy caches:
+<literal>Acquire::http::No-Cache</literal> tells the proxy not to use its
+cached response under any circumstances.
+<literal>Acquire::http::Max-Age</literal> sets the allowed maximum age (in
+seconds) of an index file in the cache of the proxy.
+<literal>Acquire::http::No-Store</literal> specifies that the proxy should not
+store the requested archive files in its cache, which can be used to prevent
+the proxy from polluting its cache with (big) .deb files.</para>
+</refsect2>
+
+<refsect2><title>Automatic Proxy Configuration</title>
+<para><literal>Acquire::http::Proxy-Auto-Detect</literal> can be used to
+specify an external command to discover the http proxy to use. The first
+and only parameter is an URI denoting the host to be contacted to allow
+for host-specific configuration. APT expects the command to output the
+proxy on stdout as a single line in the previously specified URI format
+or the word <literal>DIRECT</literal> if no proxy should be used. No output
+indicates that the generic proxy settings should be used.</para>
+<para>Note that auto-detection will not be used for a host if a host-specific proxy
+configuration is already set via <literal>Acquire::http::Proxy::<replaceable>host</replaceable></literal>.</para>
+<para>See the &squid-deb-proxy-client; and &auto-apt-proxy; packages for example implementations.</para>
+<para>This option takes precedence over the legacy option name <literal>Acquire::http::ProxyAutoDetect</literal>.</para>
+</refsect2>
+
+<refsect2><title>Connection Configuration</title>
+<para>The option <literal>Acquire::http::Timeout</literal> sets the timeout timer used by the method;
+this value applies to the connection as well as the data timeout.</para>
+<para>The used bandwidth can be limited with
+<literal>Acquire::http::Dl-Limit</literal> which accepts integer values in
+kilobytes per second. The default value is 0 which deactivates the limit and
+tries to use all available bandwidth. Note that this option implicitly
+disables downloading from multiple servers at the same time.</para>
+<para>The setting <literal>Acquire::http::Pipeline-Depth</literal> can be used to
+enable HTTP pipelining (RFC 2616 section 8.1.2.2) which can be beneficial e.g. on
+high-latency connections. It specifies how many requests are sent in a pipeline.
+APT tries to detect and workaround misbehaving webservers and proxies at runtime, but
+if you know that yours does not conform to the HTTP/1.1 specification pipelining can
+be disabled by setting the value to 0. It is enabled by default with the value 10.</para>
+<para><literal>Acquire::http::AllowRedirect</literal> controls whether APT will follow
+redirects, which is enabled by default.</para>
+<para><literal>Acquire::http::User-Agent</literal> can be used to set a different
+User-Agent for the http download method as some proxies allow access for clients
+only if the client uses a known identifier.</para>
+<para><literal>Acquire::http::SendAccept</literal> is enabled by default and
+sends a <literal>Accept: text/*</literal> header field to the server for
+requests without file extensions to prevent the server from attempting content
+negotiation.</para>
+</refsect2>
+</refsect1>
+
+<refsect1><title>Examples</title>
+<literallayout>
+Acquire::http {
+	Proxy::example.org "DIRECT";
+	Proxy "socks5h://apt:pass@localhost:9050";
+	Proxy-Auto-Detect "/usr/local/bin/apt-http-proxy-auto-detect";
+	No-Cache "true";
+	Max-Age "3600";
+	No-Store "true";
+	Timeout "10";
+	Dl-Limit "42";
+	Pipeline-Depth "0";
+	AllowRedirect "false";
+	User-Agent "My APT-HTTP";
+	SendAccept "false";
+};
+</literallayout>
+</refsect1>
+
+<refsect1>
+<title>See Also</title>
+<para>&apt-conf; &apt-authconf; &sources-list;
+</para>
+</refsect1>
+
+ &manbugs;
+
+</refentry>
diff --git a/doc/apt-verbatim.ent b/doc/apt-verbatim.ent
index 946c7cc7d..1af7b174d 100644
--- a/doc/apt-verbatim.ent
+++ b/doc/apt-verbatim.ent
@@ -81,6 +81,11 @@
   </citerefentry>"
 >
 
+<!ENTITY apt-transport-http "<citerefentry>
+    <refentrytitle><command>apt-transport-http</command></refentrytitle>
+    <manvolnum>1</manvolnum>
+  </citerefentry>"
+>
 
 <!ENTITY sources-list "<citerefentry>
     <refentrytitle><filename>sources.list</filename></refentrytitle>
@@ -148,6 +153,12 @@
   </citerefentry>"
 >
 
+<!ENTITY auto-apt-proxy "<citerefentry>
+    <refentrytitle><command>auto-apt-proxy</command></refentrytitle>
+    <manvolnum>1</manvolnum>
+  </citerefentry>"
+>
+
 <!ENTITY debsign "<citerefentry>
     <refentrytitle><command>debsign</command></refentrytitle>
     <manvolnum>1</manvolnum>
diff --git a/doc/apt.conf.5.xml b/doc/apt.conf.5.xml
index 6f47bb029..30714e66b 100644
--- a/doc/apt.conf.5.xml
+++ b/doc/apt.conf.5.xml
@@ -409,70 +409,6 @@ APT::Compressor::rev {
      be symlinked when possible instead of copying. True is the default.</para></listitem>
      </varlistentry>
 
-     <varlistentry><term><option>http</option></term>
-     <listitem><para><literal>http::Proxy</literal> sets the default proxy to use for HTTP
-     URIs. It is in the standard form of <literal>http://[[user][:pass]@]host[:port]/</literal>.
-     Per host proxies can also be specified by using the form
-     <literal>http::Proxy::&lt;host&gt;</literal> with the special keyword <literal>DIRECT</literal> 
-	 meaning to use no proxies. If no one of the above settings is specified,
-	 <envar>http_proxy</envar> environment variable
-	 will be used.</para>
-
-     <para>Three settings are provided for cache control with HTTP/1.1 compliant
-     proxy caches.
-     <literal>No-Cache</literal> tells the proxy not to use its cached
-     response under any circumstances.
-     <literal>Max-Age</literal> sets the allowed maximum age (in seconds) of
-     an index file in the cache of the proxy.
-     <literal>No-Store</literal> specifies that the proxy should not store
-     the requested archive files in its cache, which can be used to prevent
-     the proxy from polluting its cache with (big) .deb files.</para>
-
-     <para>The option <literal>timeout</literal> sets the timeout timer used by the method;
-     this value applies to the connection as well as the data timeout.</para>
-
-     <para>The setting <literal>Acquire::http::Pipeline-Depth</literal> can be used to
-     enable HTTP pipelining (RFC 2616 section 8.1.2.2) which can be beneficial e.g. on
-     high-latency connections. It specifies how many requests are sent in a pipeline.
-     APT tries to detect and workaround misbehaving webservers and proxies at runtime, but
-     if you know that yours does not conform to the HTTP/1.1 specification pipelining can
-     be disabled by setting the value to 0. It is enabled by default with the value 10.</para>
-
-     <para><literal>Acquire::http::AllowRedirect</literal> controls whether APT will follow
-     redirects, which is enabled by default.</para>
-
-     <para>The used bandwidth can be limited with
-     <literal>Acquire::http::Dl-Limit</literal> which accepts integer
-     values in kilobytes per second. The default value is 0 which
-     deactivates the limit and tries to use all available bandwidth.
-     Note that this option implicitly disables downloading from
-     multiple servers at the same time.</para>
-
-     <para><literal>Acquire::http::User-Agent</literal> can be used to set a different
-     User-Agent for the http download method as some proxies allow access for clients
-     only if the client uses a known identifier.</para>
-
-     <para><literal>Acquire::http::Proxy-Auto-Detect</literal> can be used to
-     specify an external command to discover the http proxy to use. The first
-     and only parameter is an URI denoting the host to be contacted to allow
-     for host-specific configuration. APT expects the command to output the
-     proxy on stdout as a single line in the style <literal>http://proxy:port/</literal>
-     or the word <literal>DIRECT</literal> if no proxy should be used. No output
-     indicates that the generic proxy settings should be used.
-
-     Note that auto-detection will not be used for a host if a host-specific proxy
-     configuration is already set via <literal>Acquire::http::Proxy::<replaceable>HOST</replaceable></literal>.
-
-     See the &squid-deb-proxy-client; package for an example implementation that
-     uses avahi.
-
-     This option takes precedence over the legacy option name
-     <literal>ProxyAutoDetect</literal>.
-     </para>
-
-     </listitem>
-     </varlistentry>
-
      <varlistentry><term><option>https</option></term>
 	 <listitem><para>
 	 The <literal>Cache-control</literal>, <literal>Timeout</literal>,
diff --git a/doc/po4a.conf b/doc/po4a.conf
index 955ebbc76..4b8d33f52 100644
--- a/doc/po4a.conf
+++ b/doc/po4a.conf
@@ -27,6 +27,7 @@
 [type: manpage] apt-sortpkgs.1.xml $lang:$lang/apt-sortpkgs.$lang.1.xml add_$lang:xml.add
 [type: manpage] apt-ftparchive.1.xml $lang:$lang/apt-ftparchive.$lang.1.xml add_$lang:xml.add
 [type: manpage] apt_auth.conf.5.xml $lang:$lang/apt_auth.conf.$lang.5.xml add_$lang:xml.add
+[type: manpage] apt-transport-http.1.xml $lang:$lang/apt-transport-http.$lang.1.xml add_$lang:xml.add
 
 [type: docbook] guide.dbk $lang:$lang/guide.$lang.dbk
 #                add_$lang::$lang/addendum/docbook_$lang.add
diff --git a/doc/sources.list.5.xml b/doc/sources.list.5.xml
index 694082bea..3f81dd515 100644
--- a/doc/sources.list.5.xml
+++ b/doc/sources.list.5.xml
@@ -352,17 +352,15 @@ deb-src [ option1=value1 option2=value2 ] uri suite [component1] [component2] [.
 
     <para>The currently recognized URI types are:
    <variablelist>
-    <varlistentry><term><command>http</command></term>
+    <varlistentry><term><command>http</command> (&apt-transport-http;)</term>
     <listitem><para>
     The http scheme specifies an HTTP server for an archive and is the most
-    commonly used method, with many options in the
-    <literal>Acquire::http</literal> scope detailed in &apt-conf;. The URI can
-    directly include login information if the archive requires it, but the use
-    of &apt-authconf; should be preferred. The method also supports SOCKS5 and
-    HTTP(S) proxies either configured via apt-specific configuration or
-    specified by the environment variable <envar>http_proxy</envar> in the
-    format (assuming an HTTP proxy requiring authentication)
-    <replaceable>http://user:pass@server:port/</replaceable>.
+    commonly used method. The URI can directly include login information if the
+    archive requires it, but the use of &apt-authconf; should be preferred.
+    The method also supports SOCKS5 and HTTP(S) proxies either configured via
+    apt-specific configuration or specified by the environment variable
+    <envar>http_proxy</envar> in the format (assuming an HTTP proxy requiring
+    authentication) <replaceable>http://user:pass@server:port/</replaceable>.
     The authentication details for proxies can also be supplied via
     &apt-authconf;.</para>
     <para>Note that these forms of authentication are insecure as the whole