move special READMEs into doc/ and format as md

The formatting is very basic and more should probably be done, but we at
least get the files out of the root directory which in case of the
various READMEs was confusing salsa which one display as (central) README.

7 files changed, 359 insertions, 96 deletions

diff --git a/doc/acquire-additional-files.txt b/doc/acquire-additional-files.md
index c55d5fe19..30c83ef25 100644
--- a/doc/acquire-additional-files.txt
+++ b/doc/acquire-additional-files.md
@@ -7,12 +7,12 @@ process which is hard to implement correctly and securely.
 APT front-ends share the code and binaries to make this happen in libapt
 with the Acquire system, supported by helpers shipped in the apt package
 itself and additional transports in individual packages like
-apt-transport-https.
+`apt-transport-https`.
 
-For its own operation libapt needs or can make use of Packages, Sources
-and Translation-* files, which it will acquire by default, but
-a repository might contain more data files (e.g.  Contents) a front-end
-(e.g. apt-file) might want to use and would therefore need to be
+For its own operation libapt needs or can make use of *Packages*, *Sources*
+and *Translation-* files, which it will acquire by default, but
+a repository might contain more data files (e.g. `Contents`) a front-end
+(e.g. `apt-file`) might want to use and would therefore need to be
 downloaded as well.
 
 This file describes the configuration scheme such a front-end can use to
@@ -23,8 +23,8 @@ instruct the Acquire system to download those additional files.
 The Acquire system uses the same configuration settings to implement the
 files it downloads by default. These settings are the default, but if
 they would be written in a configuration file the configuration
-instructing the Acquire system to download the Packages files would look
-like this (see also apt.conf(5) manpage for configuration file syntax):
+instructing the Acquire system to download the *Packages* files would look
+like this (see also `apt.conf(5)` manpage for configuration file syntax):
 
 	Acquire::IndexTargets::deb::Packages {
 		MetaKey "$(COMPONENT)/binary-$(ARCHITECTURE)/Packages";
@@ -37,72 +37,74 @@ like this (see also apt.conf(5) manpage for configuration file syntax):
 		Optional "no";
 	};
 
-All files which should be downloaded (nicknamed 'Targets') are mentioned
-below the Acquire::IndexTargets scope. 'deb' is here the type of the
-sources.list entry the file should be acquired for. The only other
-supported value is hence 'deb-src'. Beware: You can't specify multiple
-types here and you can't download the same (evaluated) MetaKey from
+All files which should be downloaded (nicknamed *Targets*) are mentioned
+below the `Acquire::IndexTargets` scope. `deb` is here the type of the
+`sources.list` entry the file should be acquired for. The only other
+supported value is hence `deb-src`. Beware: You can't specify multiple
+types here and you can't download the same (evaluated) `MetaKey` from
 multiple types!
 
 After the type you can pick any valid and unique string which preferable
-refers to the file it downloads (In the example we picked 'Packages').
+refers to the file it downloads (In the example we picked *Packages*).
 This string is used as identifier (if not explicitly set otherwise) for
-the target class and accessible as 'Identifier' and 'Created-By' e.g.
-in the "apt-get indextargets" output as detailed below. The identifier
+the target class and accessible as `Identifier` and `Created-By` e.g.
+in the `apt-get indextargets` output as detailed below. The identifier
 is also used to allow user to enable/disable targets per sources.list
 entry.
 
 All targets have three main properties you can define:
-* MetaKey: The identifier of the file to be downloaded as used in the
+
+* `MetaKey`: The identifier of the file to be downloaded as used in the
   Release file.  It is also the relative location of the file from the
   Release file.  You can neither download from a different server
   entirely (absolute URI) nor access directories above the Release file
   (e.g. "../../").
-* ShortDescription: Very short string intended to be displayed to the
+* `ShortDescription`: Very short string intended to be displayed to the
   user e.g.  while reporting progress. apt will e.g. use this string in
   the last line to indicate progress of e.g. the download of a specific
   item.
-* Description: A preferable human understandable and readable identifier
+* `Description`: A preferable human understandable and readable identifier
   of which file is acquired exactly. Mainly used for progress reporting
   and error messages. apt will e.g. use this string in the Get/Hit/Err
   progress lines.
   An identifier of the site accessed as seen in the sources.list (e.g.
-  "http://example.org/debian" or "file:/path/to/a/repository") is
+  `http://example.org/debian` or `file:/path/to/a/repository`) is
   automatically prefixed for this property.
 
 
 Additional optional properties:
-* Identifier: The default value is the unique string identifying this
-  file (in the example above it was 'Packages') also accessible as
-  Created-By. The difference is that using this property multiple files
+
+* `Identifier`: The default value is the unique string identifying this
+  file (in the example above it was *Packages*) also accessible as
+  `Created-By`. The difference is that using this property multiple files
   can be subsumed under one identifier e.g. if you configure multiple
-  possible locations for the files (with Fallback-Of), but the front-end
+  possible locations for the files (with `Fallback-Of`), but the front-end
   doesn't need to handle files from the different locations differently.
-* DefaultEnabled: The default value is 'yes' which means that apt will
-  try to acquire this target from all sources. If set to 'no' the user
+* `DefaultEnabled`: The default value is `yes` which means that apt will
+  try to acquire this target from all sources. If set to `no` the user
   has to explicitly enable this target in the sources.list file with the
-  Targets option(s) – or override this value in a config file.
-* Optional: The default value is 'yes' and should be kept at this value.
+  `Targets` option(s) – or override this value in a config file.
+* `Optional`: The default value is `yes` and should be kept at this value.
   If enabled the acquire system will skip the download if the file isn't
-  mentioned in the Release file. Otherwise this is treated as a hard
+  mentioned in the `Release` file. Otherwise this is treated as a hard
   error and the update process fails. Note that failures while
   downloading (e.g. 404 or hash verification errors) are failures,
   regardless of this setting.
-* KeepCompressed: The default is the value of Acquire::GzipIndexes,
-  which defaults to false. If true, the acquire system will keep the
+* `KeepCompressed`: The default is the value of `Acquire::GzipIndexes`,
+  which defaults to `false`. If `true`, the acquire system will keep the
   file compressed on disk rather than extract it. If your front-end can't
   deal with compressed files transparently you have to explicitly set
-  this option to false to avoid problems with users setting the option
-  globally. On the other hand, if you set it to true or don't set it you
+  this option to `false` to avoid problems with users setting the option
+  globally. On the other hand, if you set it to `true` or don't set it you
   have to ensure your front-end can deal with all compressed fileformats
-  supported by apt (libapt users can e.g. use FileFd, others can use
-  the cat-file command of /usr/lib/apt/apt-helper).
-* Fallback-Of: Is by default not set. If it is set and specifies another
-  target name (see Created-By) which was found in the Release file the
+  supported by apt (libapt users can e.g. use `FileFd`, others can use
+  the `cat-file` command of `/usr/lib/apt/apt-helper`).
+* `Fallback-Of`: Is by default not set. If it is set and specifies another
+  target name (see `Created-By`) which was found in the *Release* file the
   download of this target will be skipped. This can be used to implement
   fallback(chain)s to allow transitions like the rename of target files.
   The behavior if cycles are formed with Fallback-Of is undefined!
-* flat{MetaKey,Description}: APT supports two types of repositories:
+* `flatMetaKey`, `flatDescription`: APT supports two types of repositories:
   dists-style repositories which are the default and by far the most
   common which are named after the fact that the files are in an
   elaborated directory structure.  In contrast a flat-style repository
@@ -116,27 +118,28 @@ file if it is available and uncompress it for you, just as it will also
 use PDiff patching if provided by the repository and enabled by the
 user. You only have to ensure that the Release file contains the
 information about the compressed files/PDiffs to make this happen.
-*NO* properties have to be set to enable this!
+**NO** properties have to be set to enable this!
 
 
-More properties exist, but these should *NOT* be set by front-ends
+More properties exist, but these should **NOT** be set by front-ends
 requesting files. They exist for internal and end-user usage only.
 Some of these are – which are documented here only to ensure that they
 aren't accidentally used by front-ends:
-* PDiffs: controls if apt will try to use PDiffs for this target.
-  Defaults to the value of Acquire::PDiffs which is true by default.
+
+* `PDiffs`: controls if apt will try to use PDiffs for this target.
+  Defaults to the value of `Acquire::PDiffs` which is *true* by default.
   Can be overridden per-source by the sources.list option of the same
   name. See the documentation for both of these for details.
-* By-Hash: controls if apt will try to use an URI constructed from
+* `By-Hash`: controls if apt will try to use an URI constructed from
   a hashsum of the file to download. See the documentation for config
-  option Acquire::By-Hash and sources.list option By-Hash for details.
-* CompressionTypes: The default value is a space separated list of
-  compression types supported by apt (see Acquire::CompressionTypes).
+  option `Acquire::By-Hash` and sources.list option `By-Hash` for details.
+* `CompressionTypes`: The default value is a space separated list of
+  compression types supported by apt (see `Acquire::CompressionTypes`).
   You can set this option to prevent apt from downloading a compression
   type a front-end can't open transparently. This should always be
   a temporary workaround through and a bug should be reported against
   the front-end in question.
-* KeepCompressedAs: The default value is a space separated list of
+* `KeepCompressedAs`: The default value is a space separated list of
   compression types supported by apt (see previous option) which is
   sorted by the cost-value of the compression in ascending order,
   except that cost=0 "compressions" (like uncompressed) are listed last.
@@ -144,7 +147,7 @@ aren't accidentally used by front-ends:
 
 # More examples
 
-The stanzas for Translation-* files as well as for Sources files would
+The stanzas for `Translation-*` files as well as for `Sources` files would
 look like this:
 
 Acquire::IndexTargets {
@@ -176,20 +179,20 @@ by the acquire system. The following variables are known; note that
 unknown variables have no default value nor are they touched: They are
 printed as-is.
 
-* $(RELEASE): This is usually an archive- or codename, e.g. "stable" or
-  "stretch".  Note that flat-style repositories do not have an archive-
+* `$(RELEASE)`: This is usually an archive- or codename, e.g. *stable* or
+  *stretch*.  Note that flat-style repositories do not have an archive-
   or codename per-se, so the value might very well be just "/" or so.
-* $(COMPONENT): as given in the sources.list, e.g. "main", "non-free" or
-  "universe".  Note that flat-style repositories again do not really
+* `$(COMPONENT)`: as given in the sources.list, e.g. *main*, *non-free* or
+  *universe*.  Note that flat-style repositories again do not really
   have a meaningful value here.
-* $(LANGUAGE): Values are all entries (expect "none") of configuration
-  option Acquire::Languages, e.g. "en", "de" or "de_AT".
-* $(ARCHITECTURE): Values are all entries of configuration option
-  APT::Architectures (potentially modified by sources.list options),
-  e.g. "amd64", "i386" or "armel" for the 'deb' type. In type 'deb-src'
-  this variable has the value "source".
-* $(NATIVE_ARCHITECTURE): The architecture apt treats as the native
-  architecture for this system configured as APT::Architecture
+* `$(LANGUAGE)`: Values are all entries (expect *none*) of configuration
+  option `Acquire::Languages`, e.g. *en*, *de* or *de_AT*.
+* `$(ARCHITECTURE)`: Values are all entries of configuration option
+  `APT::Architectures` (potentially modified by sources.list options),
+  e.g. *amd64*, *i386* or *armel* for the *deb* type. In type *deb-src*
+  this variable has the value *source*.
+* `$(NATIVE_ARCHITECTURE)`: The architecture apt treats as the native
+  architecture for this system configured as `APT::Architecture`
   defaulting to the architecture apt itself was built for.
 
 Note that while more variables might exist in the implementation, these
@@ -198,73 +201,76 @@ you have a need for other variables contact us.
 
 # Accessing files
 
-Do NOT hardcode specific file locations, names or compression types in
+Do **NOT** hardcode specific file locations, names or compression types in
 your application! You will notice that the configuration options give
 you no choice over where the downloaded files will be stored. This is by
 design so multiple applications can download and use the same file
 rather than each and every one of them potentially downloads and uses
 its own copy somewhere on disk.
 
-"apt-get indextargets" can be used to get the location as well as other
-information about all files downloaded (aka: you will see Packages,
-Sources and Translation-* files here as well). Provide a line of the
+`apt-get indextargets` can be used to get the location as well as other
+information about all files downloaded (aka: you will see *Packages*,
+*Sources* and *Translation-* files here as well). Provide a line of the
 default output format as parameter to filter out all entries which do
-not have such a line. With --format, you can further more define your
+not have such a line. With `--format`, you can further more define your
 own output style. The variables are what you see in the output, just all
-uppercase and wrapped in $(), as in the configuration file.
+uppercase and wrapped in `$()`, as in the configuration file.
+
+To get all the filenames of all *Translation-en* files you can e.g. call:
 
-To get all the filenames of all Translation-en files you can e.g. call:
 	apt-get indextargets --format '$(FILENAME)' "Identifier: Translations" "Language: en"
 
 The line-based filtering and the formatting is rather crude and feature-
-less by design: The default format is Debian's standard format deb822
+less by design: The default format is Debian's standard format `deb822`
 (in particular: Field names are case-insensitive and the order of fields
 in the stanza is undefined), so instead of apt reimplementing powerful
 filters and formatting for this command, it is recommend to use piping
-and dedicated tools like 'grep-dctrl' if you need more than the basics
+and dedicated tools like `grep-dctrl` if you need more than the basics
 provided.
 
 Accessing this information via libapt is done by reading the
-sources.lists (pkgSourceList), iterating over the metaIndex objects this
-creates and calling GetIndexTargets() on them. See the source code of
-"apt-get indextargets" for a complete example.
+sources.lists (`pkgSourceList`), iterating over the metaIndex objects this
+creates and calling `GetIndexTargets()` on them. See the source code of
+`apt-get indextargets` for a complete example.
 
 Note that by default targets are not listed if they weren't downloaded.
-If you want to see all targets, you can use the --no-release-info, which
-also removes the Codename, Suite, Version, Origin, Label and Trusted
+If you want to see all targets, you can use the `--no-release-info`, which
+also removes the *Codename*, *Suite*, *Version*, *Origin*, *Label* and *Trusted*
 fields from the output as these also display data which needs to be
 downloaded first and could hence be inaccurate [on the pro-side: This
 mode is faster as it doesn't require a valid binary cache to operate].
-The most notable difference perhaps is in the Filename field through: By
+The most notable difference perhaps is in the *Filename* field through: By
 default it indicates an existing file, potentially compressed (Hint:
-libapt users can use FileFd to open compressed files transparently). In
-the --no-release-info mode the indicated file doesn't need to exist and
+libapt users can use `FileFd` to open compressed files transparently). In
+the `--no-release-info` mode the indicated file doesn't need to exist and
 it will always refer to an uncompressed file, even if the index would be
 (or is) stored compressed.
 
-Remarks on fields only available in (default) --release-info mode:
-* Trusted: Denotes with a 'yes' or 'no' if the data in this file is
+Remarks on fields only available in (default) `--release-info mode`:
+
+* `Trusted`: Denotes with a *yes* or *no* if the data in this file is
   authenticated by a trust chain rooted in a trusted gpg key. You should
   be careful with untrusted data and warn the user if you use it.
-* Codename, Suite, Version, Origin and Label are fields from the Release
-  file, are only present if they are present in the Release file and
-  contain the same data.
+* `Codename`, `Suite`, `Version`, `Origin` and `Label` are fields from the
+  *Release* file, are only present if they are present in the *Release* file
+  and contain the same data.
 
 Remarks on other available fields:
-* MetaKey, ShortDesc, Description, Site, Release: as defined
+
+* `MetaKey`, `ShortDesc`, `Description`, `Site`, `Release`: as defined
   by the configuration and described further above.
-* Identifier: Defaults to the value of Created-By, but can be set
+* `Identifier`: Defaults to the value of `Created-By`, but can be set
   explicitly in the configuration (see above). Prefer this field over
-  Created-By to subsume multiple file(location)s (see Fallback-Of).
-* Created-By: configuration entity responsible for this target
-* Target-Of: type of the sources.list entry
-* URI, Repo-URI: avoid using. Contains potentially username/password.
-  Prefer 'Site', especially for display.
-* Optional, DefaultEnabled, KeepCompressed: Decode the options of the
+  `Created-By` to subsume multiple file(location)s (see `Fallback-Of`).
+* `Created-By`: configuration entity responsible for this target
+* `Target-Of`: type of the sources.list entry
+* `URI`, `Repo-URI`: avoid using. Contains potentially username/password.
+  Prefer `Site`, especially for display.
+* `Optional`, `DefaultEnabled`, `KeepCompressed`: Decode the options of the
   same name from the configuration.
-* Language, Architecture, Component: as defined further above, but with
+* `Language`, `Architecture`, `Component`: as defined further above, but with
   the catch that they might be missing if they don't effect the target
-  (aka: They weren't used while evaluating the MetaKey template).
+  (aka: They weren't used while evaluating the `MetaKey` template).
 
 Again, additional fields might be visible in certain implementations,
 but you should avoid using them and instead talk to us about a portable
@@ -275,7 +281,7 @@ implementation.
 It is highly encouraged that applications talk to each other and to us
 about which files they require. It is usually best to have a common
 package ship the configuration needed to get the files, but specific
-needs might require specific solutions. Again: talk to us.
+needs might require specific solutions. Again: **talk to us**.
 
 Bad things will happen if multiple front-ends request the same file(s)
 via different targets, which is another reason why coordination is very
@@ -309,10 +315,10 @@ You can't modify the files apt has downloaded as apt keeps state with
 e.g. the modification times of the files and advanced features like
 PDiffs break.
 
-You can however install an APT::Update::Post-Invoke{-Success,} hook
+You can however install an `APT::Update::Post-Invoke{-Success,}` hook
 script and use them to copy (modified) files to a different location.
-Use 'apt-get indextargets' (or similar) to get the filenames – do not
-look into /var/lib/apt/lists directly!
+Use `apt-get indextargets` (or similar) to get the filenames – do not
+look into `/var/lib/apt/lists` directly!
 
 Please avoid time consuming calculations in the scripts and instead just
 trigger a background task as there is little to no feedback for the user
diff --git a/doc/apt-verbatim.ent b/doc/apt-verbatim.ent
index 53e8e54d4..168a39012 100644
--- a/doc/apt-verbatim.ent
+++ b/doc/apt-verbatim.ent
@@ -225,7 +225,7 @@
   </citerefentry>"
 >
 
-<!ENTITY apt-acquire-additional-files "<literal><filename>/usr/share/doc/apt-doc/acquire-additional-files.txt</filename></literal>">
+<!ENTITY apt-acquire-additional-files "<literal><filename>/usr/share/doc/apt-doc/acquire-additional-files.md.gz</filename></literal>">
 
 <!-- Boiler plate docinfo section -->
 <!ENTITY apt-email "
diff --git a/doc/external-dependency-solver-protocol.txt b/doc/external-dependency-solver-protocol.md
index 68902812c..68902812c 100644
--- a/doc/external-dependency-solver-protocol.txt
+++ b/doc/external-dependency-solver-protocol.md
diff --git a/doc/external-installation-planner-protocol.txt b/doc/external-installation-planner-protocol.md
index 4bad9da0a..4bad9da0a 100644
--- a/doc/external-installation-planner-protocol.txt
+++ b/doc/external-installation-planner-protocol.md
diff --git a/doc/json-hooks-protocol.md b/doc/json-hooks-protocol.md
new file mode 100644
index 000000000..f516c1afe
--- /dev/null
+++ b/doc/json-hooks-protocol.md
@@ -0,0 +1,159 @@
+## JSON Hooks
+
+APT 1.6 introduces support for hooks that talk JSON-RPC 2.0. Hooks act
+as a server, and APT as a client.
+
+## Wire protocol
+
+APT communicates with hooks via a UNIX domain socket in file descriptor
+`$APT_HOOK_SOCKET`. The transport is a byte stream (SOCK_STREAM).
+
+The byte stream contains multiple JSON objects, each representing a
+JSON-RPC request or response, and each terminated by an empty line
+(`\n\n`). Therefore, JSON objects containing empty lines may not be
+used.
+
+For protocol version `0.1`, each JSON object must be encoded on a single
+line.
+
+## Lifecycle
+
+The general life of a hook is as following.
+
+1. Hook is started
+2. Hello handshake is exchanged
+3. One or more calls or notifications are sent from apt to the hook
+4. Bye notification is send
+
+It is unspecified whether a hook is sent one or more messages. For
+example, a hook may be started only once for the lifetime of the apt
+process and receive multiple notificatgions, but a hook may also be
+started multiple times. Hooks should thus be stateless.
+
+## JSON messages
+
+### Hello handshake
+
+APT performs a call to the method `org.debian.apt.hooks.hello` with
+the named parameter `versions` containing a list of supported protocol
+versions. The hook picks the version it supports. The current version
+is `"0.1"`, and support for that version is mandatory.
+
+*Example*:
+
+1. APT:
+   ```{"jsonrpc":"2.0","method":"org.debian.apt.hooks.hello","id":0,"params":{"versions":["0.1"]}}```
+
+
+2. Hook:
+   ```{"jsonrpc":"2.0","id":0,"result":{"version":"0.1"}}```
+
+### Bye notification
+
+Before closing the connection, APT sends a notification for the
+method `org.debian.apt.hooks.bye`.
+
+### Hook notification
+
+The following methods are supported:
+
+1. `org.debian.apt.hooks.install.pre-prompt` - Run before the y/n prompt
+1. `org.debian.apt.hooks.install.post` - Run after success
+1. `org.debian.apt.hooks.install.fail` - Run after failed install
+1. `org.debian.apt.hooks.search.pre` - Run before search
+1. `org.debian.apt.hooks.search.post` - Run after successful search
+1. `org.debian.apt.hooks.search.fail` - Run after search without results
+
+They can be registered by adding them to the list:
+
+```AptCli::Hooks::<name>```
+
+where `<name>` is the name of the hook. It is recommended that these
+option names are prefixed with `Binary::apt`, so that they only take
+effect for the `apt` binary. Otherwise, there may be compatibility issues
+with scripts and alike.
+
+#### Parameters
+
+*command*: The command used on the command-line. For example, `"purge"`.
+
+*search-terms*: Any non-option arguments given to the command.
+
+*unknown-packages*: For non-search hooks, a subset of *search-terms*
+that APT could not find packages in the cache for.
+
+*packages*: An array of modified packages. This is mostly useful for
+install. Each package has the following attributes:
+
+- *id*: An unsigned integer describing the package
+- *name*: The name of the package
+- *architecture*: The architecture of the package. For `"all"` packages, this will be the native architecture;
+                  use per-version architecture fields to see `"all"`.
+
+- *mode*: One of `install`, `deinstall`, `purge`, or `keep`. `keep`
+          is not exposed in 0.1. To determine an upgrade, check
+          that a current version is installed.
+- *automatic*: Whether the package is/will be automatically installed
+- *versions*: An array with up to 3 fields:
+
+  - *candidate*: The candidate version
+  - *install*: The version to be installed
+  - *current*: The version currently installed
+
+  Each version is represented as an object with the following fields:
+
+  - *id*: An unsigned integer
+  - *version*: The version as a string
+  - *architecture*: Architecture of the version
+  - *pin*: The pin priority
+
+#### Example
+
+```json
+{
+    "jsonrpc": "2.0",
+    "method": "org.debian.apt.hooks.install.pre",
+    "params": {
+        "command": "purge",
+        "search-terms": [
+            "petname-",
+            "lxd+"
+        ],
+        "packages": [
+            {
+                "id": 1500,
+                "name": "ebtables",
+                "architecture": "amd64",
+                "mode": "install",
+                "automatic": 1,
+                "versions": {
+                    "candidate": {
+                        "id": 376,
+                        "version": "2.0.10.4-3.5ubuntu2",
+                        "architecture": "amd64",
+                        "pin": 990
+                    },
+                    "install": {
+                        "id": 376,
+                        "version": "2.0.10.4-3.5ubuntu2",
+                        "architecture": "amd64",
+                        "pin": 990
+                    }
+                }
+            }
+        ]
+    }
+}
+```
+
+#### Compatibility note
+Future versions of APT might make these calls instead of notifications.
+
+## Evolution of this protocol
+New incompatible versions may be introduced with each new feature
+release of apt (1.7, 1.8, etc). No backward compatibility is promised
+until protocol 1.0: New stable feature releases may support a newer
+protocol version only (for example, 1.7 may only support 0.2).
+
+Additional fields may be added to objects without bumping the protocol
+version.
diff --git a/doc/progress-reporting.md b/doc/progress-reporting.md
new file mode 100644
index 000000000..c4963af68
--- /dev/null
+++ b/doc/progress-reporting.md
@@ -0,0 +1,76 @@
+Install-progress reporting 
+--------------------------
+
+If the apt options `APT::Status-Fd` is set, apt will send status
+reports to that fd. The status information is separated with a '`:`',
+there are the following status conditions:
+
+* pmstatus
+* dlstatus
+* conffile-prompt
+* error
+* media-change
+
+The reason for using a fd instead of an OpProgress class is that many
+apt front-end fork a (vte) terminal for the actual installation.
+
+The reason to do the mapping and l10n of the dpkg states to human
+readable (and translatable) strings is that this way the translation
+needs to be done only once for all front-ends.
+
+
+pmstatus
+--------
+Status of the package manager (dpkg). This is send when packages
+are installed/removed.
+	pmstatus:pkgname:TotalPercentage:action-description
+
+* PkgName = the name of the package
+* TotalPercentage = the total progress between [0..100]
+* description = a i18ned human readable description of the current action
+
+Example:
+
+	# ./apt-get install -o APT::Status-Fd=2 3dchess >/dev/null
+	pmstatus:3dchess:20:Preparing 3dchess
+	pmstatus:3dchess:40:Unpacking 3dchess
+	pmstatus:3dchess:60:Preparing to configure 3dchess
+	pmstatus:3dchess:80:Configuring 3dchess
+	pmstatus:3dchess:100:Installed 3dchess
+
+pmerror
+-------
+	pmerror:deb:TotalPercentage:error string
+
+Example:
+
+	pmerror: /var/cache/apt/archives/krecipes_0.8.1-0ubuntu1_i386.deb : 75% : trying to overwrite `/usr/share/doc/kde/HTML/en/krecipes/krectip.png', which is also in package krecipes-data
+
+
+pmconffile
+----------
+	pmconffile:conffile:percent:'current-conffile' 'new-conffile' useredited distedited
+
+
+media-change
+------------
+	media-change:medium:drive:human-readable string
+
+Example:
+
+	media-change: Ubuntu 5.10 _Breezy Badger_ - Alpha i386 (20050830):/cdrom/:Please insert the disc labeled: 'Ubuntu 5.10 _Breezy Badger_ - Alpha i386 (20050830)' in the drive '/cdrom/' and press enter.
+
+
+dlstatus
+--------
+	dlstatus:AlreadDownloaded:TotalPercentage:action-description
+
+* AlreadyDownloaded = the number of already downloaded packages
+* TotalPercentage = the total progress between [0..100]
+* description = a i18ned human readable description of the current action
+
+Example:
+
+	dlstatus:1:9.05654:Downloading file 1 of 3 (4m40s remaining)
+	dlstatus:1:9.46357:Downloading file 1 of 3 (4m39s remaining)
+	dlstatus:1:9.61022:Downloading file 1 of 3 (4m38s remaining)
diff --git a/doc/srv-records-support.md b/doc/srv-records-support.md
new file mode 100644
index 000000000..004811cf2
--- /dev/null
+++ b/doc/srv-records-support.md
@@ -0,0 +1,22 @@
+DNS SRV record support in apt
+=============================
+
+Apt supports a subset of the DNS SRV server records protocol as
+described in [RFC 2782](https://tools.ietf.org/html/rfc2782) for service discovery.
+
+Before connecting to the requested server APT will send a SRV
+record request of the form `_$protocol._tcp._$host`, e.g.
+`_http._tcp.ftp.debian.org` or `_http._tcp.security.debian.org`.
+
+If the server sends SRV records
+as a reply APT will use those to connect to the server(s) in
+this reply. It will honor the `priority` field in the reply.
+
+However it does not implement the `weight` algorithm as described
+in RFC 2782. It will use an equal weight for each server of the
+same priority.
+
+If connecting to a server fails APT will retry with the next one
+and remove the server from the list of valid servers for this
+session.
+