+The rationale for using helper scripts in <file>debian/rules</file> is
+that lets maintainers use and share common logic among many packages.
+Take for instance the question of installing menu entries: you need to
+put the file into <file>/usr/lib/menu</file>, and add commands to the
+maintainer scripts to register and unregister the menu entries. Since
+this is a very common thing for packages to do, why should each
+maintainer rewrite all this on their own, sometimes with bugs? Also,
+supposing the menu directory changed, every package would have to be
+changed.
+ <p>
+Helper scripts take care of these issues. Assuming you comply with
+the conventions expected by the helper script, the helper takes care
+of all the details. Changes in policy can be made in the helper
+script, then packages just need to be rebuilt with the new version of
+the helper and no other changes.
+ <p>
+<ref id="tools"> contains a couple of different helpers. The most
+common and best (in our opinion) helper system is
+<package>debhelper</package>. Previous helper systems, such as
+<package>debmake</package>, were "monolithic": you couldn't pick and
+choose which part of the helper you found useful, but had to use the
+helper to do everything. <package>debhelper</package>, however, is a
+number of separate little <prgn>dh_*</prgn> programs. For instance,
+<prgn>dh_installman</prgn> installs and compresses man pages,
+<prgn>dh_installmenu</prgn> installs menu files, and so on. Thus, it
+offers enough flexibility to be able to use the little helper scripts,
+where useful, in conjunction with hand-crafted commands in
+<file>debian/rules</file>.
+ <p>
+You can get started with <package>debhelper</package> by reading
+<manref name="debhelper" section="1">, and looking at the examples
+that come with the package. <prgn>dh_make</prgn>, from the
+<package>dh-make</package> package (see <ref id="dh-make">), can be
+used to convert a "vanilla" source package to a
+<package>debhelper</package>ized package. This shortcut, though,
+should not convince you that you do not need to bother understanding
+the individual <prgn>dh_*</prgn> helpers. If you are going to use a
+helper, you do need to take the time to learn to use that helper, to
+learn its expectations and behavior.
+ <p>
+Some people feel that vanilla <file>debian/rules</file> files are
+better, since you don't have to learn the intricacies of any helper
+system. This decision is completely up to you. Use what works for
+you. Many examples of vanilla <file>debian/rules</file> files are
+available at <url id="&url-rules-files;">.
+
+
+ <sect1 id="multiple-patches">
+ <heading>Patching source versus patching at build time</heading>
+ <p>
+Big, complex packages may have many bugs that you need to deal with.
+If you correct a number of bug directly in the source, if you're not
+careful, it can get hard to differentiate the various patches that you
+applied. It can get quite messy when you have to update the package
+to a new upstream version which integrates some of the fixes (but not
+all). You can't take the total set of diffs (e.g., from
+<file>.diff.gz</file>) and work out which patch sets to back out as a
+unit as bugs are fixed upstream.
+ <p>
+One good solution is to keep separate patches under the
+<file>debian</file> directory and apply the patches at build time. The
+<package>dbs</package> package provides an convenient means for
+applying patches at build time (and unapplying them at clean time).
+<package>dbs</package> also provides facilities for creating the
+patches and keeping track of what they are for. As always when using
+maintainer tools, you'll have to read the accompanying documentation.
+The package <package>hello-dbs</package> is a simple example that
+demonstrates how to use <package>dbs</package>.
+
+
+ <sect1 id="multiple-binary">Multiple binary packages
+ <p>
+A single source package will often build several binary packages,
+either to provide several flavors of the same software (examples are
+the <package>vim-*</package> packages) or to make several small
+packages instead of a big one (e.g., if the user can install only the
+subset she needs, and thus save some disk space).
+ <p>
+The second case can be easily managed in <file>debian/rules</file>.
+You just need to move the appropriate files from the build directory
+into the package's temporary trees. You can do this using
+<prgn>install</prgn> (vanilla approach) or <prgn>dh_install</prgn>
+(from <package>debhelper</package>). Be sure to check the different
+permutations of the various packages, ensuring that you have the
+inter-package dependencies set right in <file>debian/control</file>.
+ <p>
+The first case is a bit more difficult since it involves multiple
+recompiles of the same software but with different configure
+options. The <package>vim</package> is an example of how to manage
+this using an hand-crafted <file>debian/rules</file> file.
+
+<!-- &FIXME; Find a good debhelper example with multile configure/make
+ cycles -->
+ </sect1>
+ </sect>
+
+ <sect id="bpp-debian-maint-scripts">
+ <heading>Best practices for maintainer scripts</heading>
+ <p>
+Maintainer scripts include the files <file>debian/postinst</file>,
+<file>debian/preinst</file>, <file>debian/prerm</file> and
+<file>debian/postrm</file>. These scripts take care of any package
+installation or deinstallation setup which isn't handled merely by the
+creation or removal of files and directories. The following
+instructions supplement the <url id="&url-debian-policy;" name="Debian
+Policy">.
+ <p>
+Maintainer scripts must be idempotent. That means that you need to
+make sure nothing bad will happen if the script is called twice where
+it would usually be called once.
+ <p>
+Standard input and output may be redirected (e.g. into pipes) for
+logging purposes, so don't rely on them being a tty.
+ <p>
+All prompting or interactive configuration should be kept to a
+minimum. When it is necessary, you should use the
+<package>debconf</package> package for the interface. Remember that
+prompting in any case can only be in the <tt>configure</tt> stage of
+the <file>postinst</file> script.
+ <p>
+Keep the maintainer scripts as simple as possible. We suggest you use
+pure POSIX shell scripts. Remember, if you do need any bash features,
+the maintainer script must have a bash sh-bang line. POSIX shell or
+Bash are preferred to Perl, since they enable
+<package>debhelper</package> to easily add bits to the scripts.
+ <p>
+If you change your maintainer scripts, be sure to test package
+removal, double installation, and purging. Be sure that a purged
+package is completely gone, that is, it must remove any files created,
+directly or indirectly, in any maintainer script.
+ <p>
+If you need to check for the existence of a command, you should use
+something like
+<example>if [ -x /usr/sbin/install-docs ]; then ...</example>
+
+If you don't wish to hard-code the path of the command in your
+maintainer script, the following POSIX-compliant shell function may
+help:
+
+&example-pathfind;
+
+You can use this function to search <tt>$PATH</tt> for a command name,
+passed as an argument. It returns true (zero) if the command was
+found, and false if not. This is really the most portable way, since
+<tt>command -v</tt>, <prgn>type</prgn>, and <prgn>which</prgn> are not
+POSIX. While <prgn>which</prgn> is an acceptable alternative, since
+it is from the required <package>debianutils</package> package, it's
+not on the root partition, although that is probably not something
+that will cause a problem.
+
+
+ <sect id="bpp-debian-control">
+ <heading>Best practices for <file>debian/control</file></heading>
+ <p>
+The following practices supplement the <url
+ id="&url-debian-policy;ch-miscellaneous.html#s-descriptions"
+ name="Policy on package descriptions">.</p>
+
+ <sect1 id="bpp-pkg-desc">
+ <heading>Writing useful descriptions</heading>
+ <p>
+The description of the package (as defined by the corresponding field
+in the <file>control</file> file) is the primary information available
+to the user about a package before they install it. It should provide
+all the required information to let the user decide whether to install
+the package.
+ <p>
+For consistency and aesthetics, you should capitalize the first letter
+of the Synopsis. Don't put a full stop (period) at the end. The
+description itself should consist of full sentences.
+ <p>
+Since the first user impression is based on the description, be
+careful to avoid spelling and grammar mistakes. Ensure that you
+spell-check it. <prgn>ispell</prgn> has a special <tt>-g</tt> option
+for <file>debian/control</file> files:
+
+<example>ispell -d american -g debian/control</example>
+
+If you want someone to proofread the description that you
+intend to use you may ask on &email-debian-l10n-english;.
+ </sect1>
+
+ <sect1 id="bpp-upstream-info">
+ <heading>Upstream home page</heading>
+ <p>
+We recommend that you add the URL for the package's home page to the
+package description in <file>debian/control</file>. This information
+should be added at the
+end of description, using the following format:
+
+<example> .
+ Homepage: http://some-project.some-place.org/</example>
+
+Note the spaces prepending the line, which serves to break the lines
+correctly. To see an example of how this displays, see <url
+id="&url-eg-desc-upstream-info;">.
+ <p>
+If there is no home page for the software, this should naturally be
+left empty.
+ <p>
+Note that we expect this field will eventually be replaced by a proper
+<file>debian/control</file> field understood by <prgn>dpkg</prgn> and
+<tt>&packages-host;</tt>. If you don't want to bother migrating the
+home page from the description to this field, you should probably wait
+until that is available.</p>
+ </sect1>
+ </sect>