<chapter id="gbp.intro">
    <title>Introduction</title>
    <para>
      Welcome to git-buildpackage (short &gbp;), a system that integrates the
      <ulink url="https://www.debian.org/">Debian</ulink> package build
      system with <ulink url="https://git-scm.com/doc">Git</ulink>. The most
      recent version of this manual can be found at &manual;.
    </para>
    <para>
      This is what &gbp; can do for you:
    </para>
    <itemizedlist>
      <listitem><para>Import existing &debian; packages into &git;</para></listitem>
      <listitem><para>Incrementally import new versions of a Debian
      package into &git; e.g. for importing NMUs or to maintain
      downstream modifications</para></listitem>
      <listitem><para>Import new upstream versions from tarballs or git tags, or both at the same time</para></listitem>
      <listitem><para>Automatically apply debian/copyright filters for DFSG-clean imports</para></listitem>
      <listitem><para>Recreate (bit-for-bit with pristine-tar) the upstream tarball from information stored in &git;</para></listitem>
      <listitem><para>Maintain a consistent branch and tag naming within a &git; repository, across
	  repositories or across a team of developers</para></listitem>
      <listitem><para>Automatically sign generated tags</para></listitem>
      <listitem><para>Make sure you have committed all changes to the right
	  branch before building and releasing</para>
      </listitem>
      <listitem><para>Execute hooks at various points of the package
	  build process e.g. to automatically push changes to remote
	  repositories</para>
      </listitem>
      <listitem><para>Integrate the build process with cowbuilder or other builders</para></listitem>
      <listitem><para>Export to a clean build area before building the package</para></listitem>
      <listitem><para>Generate <filename>debian/changelog</filename> automatically</para></listitem>
      <listitem><para>Add, edit and rebase the <filename>debian/patche</filename> without having to use GNU Quilt</para></listitem>
      <listitem>
        <para>
          Pull changes from remote repositories like
          <ulink url="https://salsa.debian.org/">salsa.debian.org</ulink>
        </para>
      </listitem>
      <listitem>
        <para>
          Publish changes to remote packaging repositories like
          <ulink url="https://salsa.debian.org/">salsa.debian.org</ulink>
        </para>
      </listitem>
    </itemizedlist>
   <para>
    All of this is (hopefully) being done without restricting the user to certain usage patterns.
    </para>
    <para>
      Git-buildpackage utlizises among others
      <ulink url="https://manpages.debian.org/unstable/devscripts/uscan.1.en.html">uscan</ulink>,
      <ulink url="https://manpages.debian.org/unstable/pristine-tar/pristine-tar.1.en.html">pristine-tar</ulink>,
      <ulink url="https://manpages.debian.org/unstable/devscripts/debchange.1.en.html">debchange</ulink>
      and <ulink url="https://manpages.debian.org/unstable/devscripts/debuild.1.en.html">debuild</ulink>
      (which in turn uses
      <ulink url="https://manpages.debian.org/unstable/dpkg-dev/dpkg-buildpackage.1.en.html">dpkg-buildpackage</ulink>
      and <ulink url="https://manpages.debian.org/unstable/lintian/lintian.1.en.html">lintian</ulink>).
      Prior knowledge about these tools transfer easily to git-buildpackage as
      for example the configuration options have the same names. However, people
      learning Debian packaging do not need to know these tools as
      git-buildpackage will by default use these tools correctly on behalf of
      the user. Leveraging on these tools also means that git-buildpackage has
      all the capabilities these tools have, and git-buildpackage is equally
      compliant to all Debian policies as these tools are.
    </para>

<sect1 id="gbp.repository">
	<title>Repository Layout and Terminology</title>
	<para>It is recommended to have the &debian; packaging on a separate
	branch than the upstream source <footnote><para>this, of course, has
	no meaning for &debian; native packages</para></footnote>.
	This is necessary to be able to import
	and merge in new upstream versions via &gbp-import-orig;.
	To distinguish these two branches, the following terminology
	<footnote><para>corresponding to the command
	line and config file options</para></footnote> is used:
	</para>
	<itemizedlist>
	<listitem><para>The <option>debian-branch</option> (the default branch name
	used in the &git; repository is <emphasis>master</emphasis> and in DEP-14
	<emphasis>debian/latest</emphasis>) holds your current development work.
	That's the branch you usually cut your releases from and the default branch
	new upstream releases are merged onto.</para></listitem>

	<listitem><para> The <option>upstream-branch</option> (the default branch name
	used in the &git; repository is <emphasis>upstream</emphasis> and in DEP-14
	<emphasis>upstream/latest</emphasis>) holds the upstream releases. Note that
	this branch is to contain the upstream source code as it was at the time of
	the upstream release, which was imported into Debian packaging. It is not
	intended to point to the tip of the upstream development branch. The branch
	contents is updated by extracting the upstream source tarball into it, or by
	pulling from an upstream release tag.</para></listitem>

	<listitem><para> The <option>pristine-tar branch</option> (the default
	branch name used in the &git; repository is
	<emphasis>pristine-tar</emphasis>) holds the necessary additional
	information to recreate the original tarball from the
	<option>upstream-branch</option>. In order to use this feature, you need
	to install the &pristine-tar; package.</para></listitem>

	<listitem><para> There can be one or more <option>patch-queue</option> branches.
	Every patch-queue branch is related to a
	<option>debian-branch</option>. If the <option>debian-branch</option> is called
	<emphasis>master</emphasis>, the corresponding patch-queue branch is
	called <emphasis>patch-queue/master</emphasis>. The patch-queue branch is
	the &debian; branch plus the contents of
	<emphasis>debian/patches</emphasis> applied. These branches are managed
	with &gbp-pq;.
	</para></listitem>
	</itemizedlist>

	<para>You're completely
	free to pick any repository layout; the branch names above are only
	&gbp;'s defaults. They can be changed at any point in time,
	and you can work with an arbitrary number of branches.
	For example, branches like <emphasis>nmu</emphasis>,
	<emphasis>backports</emphasis> or <emphasis>stable</emphasis> might
	(temporarily or permanently) become your <option>debian-branch</option>,
	and branches like <emphasis>dfsg</emphasis> or
	<emphasis>snapshots</emphasis> might become your
	<option>upstream-branch</option>&mdash;it doesn't matter if these branches
	are maintained with &gbp-import-orig; or not.</para>
        <para>
        A flexible, recommended branch layout compatible with DEP-14 is
        described in the section <xref linkend="gbp.branch.naming"/>.
        </para>
	<para>Since &gbp-buildpackage; only works with local &git;-repositories,
	you have to use <command>git push</command> or <command>gbp
        push</command>in order to publish your changes to remote repositories
        like <ulink
	url="https://salsa.debian.org/">salsa.debian.org</ulink>; this can be
	automated with &gbp-buildpackage;'s <option>post-tag</option>
	hook.</para>
</sect1>

<sect1 id="gbp.workflow">
    <title>Workflow</title>
    <para>
    	A typical, simple workflow consists of the following steps:
    </para>
    <orderedlist>
	<listitem><para>Initially import a  &debian; package via &gbp-import-dsc;. This
	imports the &debian; Package on the <option>debian-branch</option>
	and the upstream sources on the <option>upstream-branch</option>.</para></listitem>
	<listitem><para>Develop, test, commit changes. During this time, you can
	always build the package with &gbp-buildpackage;. In case you have
	uncommitted changes in your source tree, you can use the
	<option>--git-ignore-new</option> option.</para></listitem>
	<listitem><para>Optionally you can create the &debian; changelog entries
	using &gbp-dch; and create snapshot releases for testing using its
	<option>--snapshot</option> option.</para></listitem>
	<listitem><para>Once satisfied, you can build the final package with
	&gbp-buildpackage; <option>--git-tag</option>. This additionally
	creates a tag within &git; so you can switch back to that version later
	at any time. The format of the tags can be specified; tags can
	be &gpg; signed.</para></listitem>
	<listitem><para>When a new upstream version is released and upstream
	isn't using &git;, you can import the new version via &gbp-import-orig;
	onto the <option>upstream-branch</option>.  &gbp-import-orig; will
	by default try to merge the new upstream version onto the
	<option>debian-branch</option> (you can skip the merge with
	<option>--no-merge</option>).  After resolving any potential conflicts,
	go back to the second step.</para></listitem>
    </orderedlist>
    <para>These steps will be explained in more details in the following sections.</para>
</sect1>

</chapter>
