r136 - /web/deps/dep6.mdwn

[dapal at users.alioth.debian.org]

Author: dapal
Date: Sun Dec 20 15:20:08 2009
New Revision: 136

URL: http://svn.debian.org/wsvn/dep/?sc=1&rev=136
Log:
Add draft for DEP-6

Added:
    web/deps/dep6.mdwn

Added: web/deps/dep6.mdwn
URL: http://svn.debian.org/wsvn/dep/web/deps/dep6.mdwn?rev=136&op=file
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--- web/deps/dep6.mdwn (added)
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+[[!meta title="DEP-6: Meta-Package debian/control field"]]
+
+	Title: Meta-Package debian/control field
+	DEP: 6
+	State: DRAFT
+	Date: 2009-12-20
+	Drivers: David Paleino <dapal at debian.org>, Luca Bruno <lethalman88 at gmail.com>
+	URL: http://dep.debian.net/deps/dep6
+	License:
+	 Copying and distribution of this file, with or without modification,
+	 are permitted in any medium without royalty provided the copyright
+	 notice and this notice are preserved.
+	Abstract:
+	 Introduce the usage of a new field in debian/control, Meta-Package,
+	 to mark "meta-packages" as such, and allow easy choice of
+	 installed packages, without being bitten by the "autoremove"
+	 feature of package management tools.
+
+[[!toc ]]
+
+# Introduction
+This document proposes a new field for debian/control, to be used in
+the so-called "meta-packages". A meta-package is a package which does
+not contain any files to be installed. Instead it has dependencies to
+other packages. There are several uses for metapackages, for example
+to provide a Desktop Environment with some default applications
+installed.
+
+# Rationale
+With the *autoremove* command being now widely used, it can become
+difficult for a user to install a meta-package but some packages it
+depends on.
+
+In fact, when removing any dependency of the meta-package, it gets
+removed as well, and all other dependencies become *leaf packages* that
+autoremove will try to remove from the system. This is usually not
+what the user wants, as she probably installed (or had it by default)
+the meta-package to have a "standard" environment, but doesn't want or
+need specific packages.
+
+With the current situation, the only solution is to specify as
+*manually installed* the packages the user wants to keep on her system.
+
+This document thus tries to introduce a new mechanism for
+meta-packages, which would be marked with **Meta-Package: yes** in the
+debian/control control file, and whose dependencies removal would not
+cause the dependant removal. Think of this as a new Recommends field,
+which cannot be controlled via /etc/apt/preferences (or similar
+configuration file).
+
+# Backwards Compatibility
+We started thinking about "Meta-Depends" fields, but soon abandoned the
+idea. This is because this field would break existing package managers
+which haven't implemented yet this DEP. That's why we chose to keep
+Depends, and add an extra field, called **Meta-Package**.
+
+# Implementation
+## Packages
+Meta-packages should use **Meta-Package: yes** in a binary stanza in the
+*debian/control* file.
+
+## Package managers
+Package managers, upon removal of any package, should check dependant
+packages, and act accordingly.
+
+If any dependant package is a meta-package, as defined by this
+document, it should **NOT** be removed, opposed to what the current
+implementations do. The package manager should then add the removed
+package to a "blacklist" for the dependant meta-package. This allows
+for upgrades of the meta-package without re-installing everything again,
+i.e. the package manager should check the dependencies of the
+meta-package against its blacklist, if present.
+
+If the Meta-Package field is not present, then the package manager
+should act normally, without any modification from the current
+behaviour.
+
+If the meta-package is removed, all its dependencies are marked for
+auto-removal, following the current behaviour.
+
+### Blacklist management
+Package managers should allow for deletion of the blacklist upon
+removal of the meta-package.
+
+Moreover, they should allow the deletion of the blacklist, and the
+installation of the missing meta-package dependencies at the same time.
+
+# Tools support
+## apt-get
+None.
+
+## aptitude
+None.
+
+## cupt
+None.
+
+## smart
+None.