// -*- Doc -*-
= Ben's reference manual
Mehdi Dogguy and Stéphane Glondu
v{localrevision}

Manual's licence

This manual is free software; you may redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

This is distributed in the hope that it will be useful, but without
any warranty; without even the implied warranty of merchantability or
fitness for a particular purpose. See the GNU General Public License
for more details.

A copy of the GNU General Public License is available as
/usr/share/common-licenses/GPL-2 in the Debian GNU/Linux distribution
or on the World Wide Web at the GNU web site. You can also obtain it
by writing to the Free Software Foundation, Inc., 51 Franklin Street,
Fifth Floor, Boston, MA 02110-1301, USA.

WARNING: This document is still work in progress!

:numbered!:
[abstract]
== Introduction
_Ben_ is the name of a set of utilities written in
http://caml.inria.fr[OCaml] and available through the `ben`
command. The major feature of _Ben_ is to provide a full featured
transition tracker to follow the evolution of a set of packages in the
Debian archive.

The aim of this document is to describe the features of _Ben_ and its
configuration.

:numbered:

== Getting the source code
_Ben_ is maintained in a Git repository available online at
https://salsa.debian.org/debian/ben. Getting the
sources is as simple as:

[source,shell]
----
git clone https://salsa.debian.org/debian/ben
----

The source tree has a `debian/` directory. It is a native
Debian package, so you can use the standard building tools in order to
build it.

== Query language

The main feature of _Ben_ is a transition tracker. The
transition tracker selects a set of affected packages and computes a
state for each of them. There exist already various ways to do
that. One solution would be to use the
https://packages.debian.org/sid/dctrl-tools[dctrl-tools]. We chose to
make our own language. This allows us to perform more fine-grained
queries, optimize queries and extend the query language easily.

A ben query is described by the following
https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form[BNF] formulae:

 <query> ::= true
           | false
           | ! <query>            /* Boolean negation     */
           | <query> '|' <query>  /* Boolean OR operator  */
           | <query> & <query>    /* Boolean AND operator */
           | ( <query> )
 /*set 2*/ | <field> ~ /<regex>/
           | <field> ~ "<list>"
           | source
           | <comparison> "<string>"
           | <field> ~ "<string>" <comparison> "<string>"

 <field> ::= .<string>

 <list>  ::= <string>
           | <string> '|' <list>

 <comparison> ::= '<<' | '<' | '>' | '>>' | '=' | '<=' | '>='

The first rules are the usual boolean constants and operators. The
sixth rule is useful to group queries and override boolean operators'
priotity.

The second set are the various type of queries implemented to match
against different criteria. It matches against a package field (in
lowercase).

We believe the syntax of queries is easy to grasp. Nonetheless,
here are some exemples:

- `.build-depends ~ /lib.*ocaml-dev/` +
  This query matches all packages that build-depend on a package
  whose name matches the http://perldoc.perl.org/perlre.html[Perl
  regular expression] `lib.*ocaml-dev`.

- `.depends ~ "libapt-pkg4.12"` +
  This one is simpler than the first one in the sense that
  `libapt-pkg4.12` is considered as a plain string and not a regular
  expression.

IMPORTANT: Note the symbols around the selectors: /.../ for
regular expressions and "..." for plain strings.

WARNING: Packages fields may contain a list of values
comma-separated. _Ben_ splits the list before looking with
"..." for a match.

- `>= "3.0"` +
  The query `>= "3.0"` matches all packages with a version number
  equal to or higher than "3.0".

- `source` +
  This matches all source packages.

Now that the concept of query is explained, we will focus on other
parts of _Ben_. We will see how we can use the queries for each
frontend.

== Frontends
_Ben_ is a set of utilities available through the `ben` command. Each
utility is called a _frontend_ and there are four:

* `download`
* `query`
* `monitor`
* `tracker`
* `rebuild`

All frontends share a set of options and each one defines its own
specific set. The shared set of command-line options is:

[options="header"]
|===
| Option                | Action
| --no-benrc            | Do not read .benrc file at startup
| --dry-run\|-n         | Dry run
| --parallel\|-P        | Set parallelism level
| --quiet\|-q           | Quiet mode
| --verbose             | Verbose mode
| --mirror uri          | Package mirror to use
| --mirror-binaries uri | Package mirror to use for binaries
| --mirror-sources  uri | Package mirror to use for sources
| --areas a,...         | Areas to consider (comma separated)
| --archs a,...         | Architectures to consider (comma separated)
| --suite a             | Suite
| --cache-dir d         | Path to cache dir
| --cache\|-C f         | Specify the name of the cache file
| --use-cache           | Use cache whenever possible
| --config\|-c c        | Config file
| --more-binary-keys l  | Comma separated list of further relevant binary keys
| --more-source-keys l  | Comma separated list of further relevant source keys
| --preferred-compression-format\|-z format | Preferred compression format (Default: Gzip)
| --version\|-V         | Display version number (and build date) and exit.
|===

NOTE: The order of command-line flags is significant. More specifically, --config
specifies a configuration file which may set other configuration keys (e.g.: areas,
archs, suite, etc...).

Ben knows about the following compression formats: Gzip, Bz2, Xz and Plain (for
no compression).

By default, Ben keeps the following defined subset of field names. In fact, there
are two subsets. The first one is for binary packages (Package, Source, Version,
Maintainer, Architecture, Provides, Depends, Pre-Depends, Conflicts, Breaks) and
the second one for source packages (Package, Source, Version, Maintainer, Binary,
Build-depends, Build-depends-indep, Build-depends-arch). If your analysis requires
more fields, you may use --more-binary-keys and --more-source-keys command-line flags
to specify your needs.

The rest of this section describes each frontend.

=== download

This frontend is the simplest one as it has no command-line options,
except the shared ones. It downloads all Sources.gz files and all
Packages.gz files for selected architectures and areas. You may
invoke it by running:

 $ ben download [options]

The requested files will be downloaded in $BEN_CACHE_DIR, if set, or
in the current directory.

NOTE: `ben download` doesn't read `ben.cache` files yet.

=== query

This utility is pretty much like
http://man.cx/grep-dctrl(1)[`grep-dctrl(1)`]. Given a list of Packages
or Sources files, it performs a query and outputs the result.

Using it is as simple as shown below:

 $ ben query ".package ~ /gentoo/" Packages

Other valid uses:

 $ zcat Packages.gz | ben query ".package ~ /gentoo/" -
 [...]
 $ ben query ".package ~ /gentoo/" Packages_foo.gz Packages_bar.bz2 Packages_baz.xz
 [...]
 $ ben query ".package ~ /gentoo/" monitor.cache
 [...]

Just like `grep-dctrl(1)`, `ben query` has a simple mechanism to
filter its output. Using the command-line option `-s`, one can specify
a comma-separated list of fields that will be shown for matching
paragraphs.

 $ ben query ".package ~ /gentoo/" -s Package,Version ...

TIP: ben query considers files matching `[sS]ources.*` to be Sources
files, to be able to make the distinction with Packages files. This is
useful especially when you use the `source` predicate.

While other frontends can take advantage from multi-core architectures, ben
query is still sequential. This may be fixed in future versions.

=== monitor

The `monitor` fontend builds a monitoring page for a transition. A
transition is described by three queries:

* `is_affected`: matches source packages that are part of this
  transition; this query is evaluated against all source and binary
  packages and, for binary packages, their source package is picked;
* `is_good`: matches binary packages that are considered to be
  ready (fixed) for this transition;
* `is_bad`: matches binary packages that are considered to be broken
  (not fixed) for this transition.

Note that some packages can be neither good nor bad. For example, there
are many packages that build-depend on some library but do not link
against it. Thus, they do not need any dependency on the library at
runtime.

Following previously defined criteria, packages will be divided into 4
categories:

* Good (✔) packages, matching `is_good` criterion
* Bad (✘) packages, matching `is_bad` criterion
* Partial (⁈) packages, matching both `is_good` and `is_bad` criteria
* Unknown state, mathing neither `is_good` nor `is_bad`

An example of a complete description of a transition is:

  is_affected = .build-depends ~ /libicu-dev/;
  is_good = .depends ~ /libicu44/;
  is_bad = .depends ~ /libicu42/;

There are other optional fields:

* `title` +
  This puts a nice title in the HTML page.

* `notes` +
  This can be used to put
  remarks about the transition or notes about the status of some
  packages or the whole transition. +
  +
  _Ben_ recognizes some special texts and turns them into links.
  The following formats are recognized:

[options="header"]
|=========================================================================
| Original text          | Result
| pts:ocaml              | https://tracker.debian.org/ocaml[pts:ocaml]
| buildd:ocaml           | https://buildd.debian.org/ocaml[buildd:ocaml]
| #123456                | https://bugs.debian.org/123456[#123456]
| <msg-id>               | https://lists.debian.org/msg-id
| $$http://example.com$$ | http://example.com
|=========================================================================

`monitor` understands the following list of command-line options:

[options="header"]
|=========================================================================
| Option                  | Action
| --run-debcheck          | Run dose-debcheck and add virtual `.uninstallable` field
| --use-projectb          | Get package lists from Projectb database
| --output\|-o file       | Select output file
| --output-format\|-f fmt | Select output format
| --stdin                 | Use stdin to read the input file
| --template template     | Select an HTML template
|=========================================================================

Output can be formatted in simple text (`text`), colored text (`color`),
Xhtml (`xhtml`), Json (`json`) or dependency levels (`levels`). `html` is
an alias for `xhtml`.

=== tracker

This frontend uses `monitor` to generate a summary page about all
known transitions. An example of such summary can be found at
https://release.debian.org/transitions/.

`tracker` has a notion of `profiles` that gives a hint on the
actual state of the transition. The default profiles are:

 * `planned` for known planned transitions or requested but not
   processed or acknowledged yet;

 * `permanent` is a special profile made to keep an eye on some set of
   packages, not necessarily a transition;

 * `ongoing` for the actual list of (known) on-going transitions;

 * `finished` has a list of some transitions that are almost finished
   (e.g. new binary packages migrated but old binary packages left in
   testing to not decrease installability, or a finished transition
   with a number of still broken packages in testing).

Technically, each `profile` is a sub-directory of the global config
directoryfootnote:[https://release.debian.org/transitions/config/]. The
latter can be specified by a command-line option.

By default, `tracker` looks for a directory named `config` which
should contain a file named `global.conf`, unless otherwise told. It
reads data (`.ben` files) from the `config` directory and outputs the
result in the `base` directory.

`tracker` has the following command-line options:

[options="header"]
|====================================================================
| Option                  | Action
| --base\|-b [dir]        | Specifies the "base" directory
| --config-dir\|-cd [dir] | Location of ben trackers
| --global-conf\|-g       | Specify tracker's global configuration file
| --transition\|-t [profile/transition] | Generate only that tracker page
| --update\|-u            | Updates cache files
| --use-projectb          | Get package lists from Projectb database
| --template template     | Select an HTML template
| --no-clean              | Leave unknown generated HTML files
|====================================================================

==== HTML Templates

Ben has a simple templating mechanism to generate customized HTML
pages. Templates are loaded dynamically when `monitor` or `tracker`
frontends are used. When none specified, Ben chooses to load the
Debian template.

You can write your own HTML template for Ben. All you have to do is to
install the package `libben-ocaml-dev` which provides the Ben
library. We recommend users to start from an existing template to ease
the task. You can compile a template (e.g. named `foo`) by running the
following commands:

 $ ocamlbuild -pkg ben foo.cmx
 $ ocamlopt -shared -o foo.cmxs _build/foo.cmx

NOTE: .cmxs files are native dynamically loadable shared modules. If
you're building on a bytecode-only architecture, you should build a
`foo.cma` instead.

If your template needs a CSS (Cascading Style Sheets) or some images,
you should install them under `/usr/share/ben/media`.

=== rebuild

This frontend recompiles a set of packages matching a query,
respecting the order of build-dependencies inside the set. It takes
as command-line argument a configuration file with the following keys:

* `is_affected`: the query used to select packages;
* `rebuild_command`: the command used to rebuild a given package.

It outputs in Makefile syntax the dependency graph of packages that
could not be built.

=== migrate

This frontend simulates a migration of some packages from unstable to
testing. It is useful to investigate Britney's behaviour. It outputs
information related to the migration of the given packages, the
resulting Sources and Packages_* files, and an easy hint.

Note that the generated hint is not guaranteed to succeed. Moreover,
this command does not take into account ages, RC bugs, tests... as
Britney does.

A typical workflow is:

 $ cd /an/empty/working/dir
 $ source /usr/share/doc/ben/examples/migrate/functions.sh
 $ update
 $ migrate package1 package2 package3
 $ debcheck

If the `debcheck` function above does not report significant
differences, there are good chances that the generated hint will
succeed. However, in this situation, Britney usually manages to
migrate the packages on its own.

== Reporting issues

Please report bugs against _Ben_ through the Debian BTS. Reported bugs
can be seen on https://bugs.debian.org/cgi-bin/pkgreport.cgi?repeatmerged=no&src=ben
