<chapter id="gbp.import">
    <title>Importing Sources</title>

    <sect1 id="gbp.import.existing">
    <title>Importing already existing &debian; packages</title>
    <para>Importing an already existing &debian; package into a &git; repository is as easy as:
<programlisting>
  &gbp-import-dsc; package_0.1-1.dsc
</programlisting>
    This will create a new &git; repository named after the imported package, put
    the upstream sources onto the <option>upstream-branch</option> and the
    &debian; patch on the <option>debian-branch</option>. In case of a &debian;
    native package, only the <option>debian-branch</option> is being used.
    You can specify alternative branch names via the
    <option>--upstream-branch</option> and <option>--debian-branch</option>
    options, or via the <option>upstream-branch</option> and
    <option>debian-branch</option> options in the configuration file.
    </para>
    <para>
    If you want to be able to exactly recreate the original tarball
    (orig.tar.gz) from &git;, you should also specify the
    <option>--pristine-tar</option> option.  This is recommended.
    </para>
    <para>
    If you want to import further versions, you can change into your shiny new
    &git; repository and just continue with the same command:
<programlisting>
  cd package/
  &gbp-import-dsc; package_0.1-2.dsc
  &gbp-import-dsc; package_0.1-3.dsc
  &gbp-import-dsc; package_0.2-1.dsc
</programlisting>
    </para>
    <para>
Or you can import all versions at once using &gbp-import-dscs;:
<programlisting>
  &gbp-import-dscs; /path/to/history/package_*.dsc
</programlisting>
This will create a &git; repository if necessary and import all versions sorted
by version number.
    </para>
    <para>You can also import all versions of a package known from the
    <ulink url="http://snapshot.debian.org/">snapshot.debian.org</ulink> service
    using the <option>--debsnap</option> option of &gbp-import-dscs;:
<programlisting>
  &gbp-import-dscs; --debsnap package
</programlisting>
    </para>
    </sect1>

    <sect1 id="gbp.import.new.upstream">
    <title>Importing a new upstream version</title>
    <para>Change into your &git; repository (which can be empty), make sure it
    has all local modifications committed, and run either of:
<programlisting>
  &gbp-import-orig; <filename>/path/to/package_0.2.orig.tar.gz</filename>
  &gbp-import-orig; <filename>/path/to/package_0.2.tar.bz2</filename>
  &gbp-import-orig; <filename>/path/to/package-0.2/</filename>
</programlisting>
    This puts the upstream sources onto the <option>upstream-branch</option> and
    tags them accordingly (the default tag format is
    <replaceable>upstream/%(version)s</replaceable>).
    </para>
    <para>
      The result is then placed onto
      the <option>debian-branch</option>. The way this happens is
      determined by the <option>--merge-mode</option> option. The
      default mode <option>auto</option> replaces the upstream sources
      while preserving the <filename>debian/</filename> directory for
      3.0 (quilt) packages. A &git; merge is used for all other source
      format versions.
    </para>
    <para>
      You can again specify different branch names via
      the <option>--upstream-branch</option> and
      <option>--debian-branch</option> options.
    </para>
    <para>If you are using <filename>debian/watch</filename> to keep
    track of how to retrieve upstream sources, you can simply use
    the <option>--uscan</option> option to download and import the
    latest upstream version:
<programlisting>
  &gbp-import-orig; --uscan
</programlisting>
    </para>
    <para>You can also filter out content
    you don't want imported:
<programlisting>
  &gbp-import-orig; <option>--filter</option>=<replaceable>'CVS/*'</replaceable> <filename>/path/to/package_0.2.orig.tar.gz</filename>
</programlisting>
    The <option>--filter</option> option can be used multiple times for more
    complex filtering.
    </para>
    <para>
    If you expect a merge conflict, you can delay the merge to the
    <option>debian-branch</option> via the <option>--no-merge</option> option and pull in
    the changes from the <option>upstream-branch</option> later.
    </para>
    <para>
    If you want to be able to exactly recreate the original tarball
    (orig.tar.gz) from &git;, you should also specify the
    <option>--pristine-tar</option> option.  This is recommended.
    </para>
    <para>To customize the commit message used by &gbp-import-orig;, use
    the <option>--import-msg</option> option. This string is a
    &pyformat;, into which the
    <replaceable>version</replaceable> variable is
    interpolated. (i.e., use <replaceable>%(version)s</replaceable> in
    your message to get the imported upstream version).
    </para>

    <sect2 id="gbp.import.error.recovery">
      <title>Recovering from errors</title>
      <para>In case of an error &gbp-import-orig; will by default
	rollback (undo) all changes it has done to the repository so far:
      </para>
      <programlisting>
	$ &gbp; import-orig --verbose --filter='CVS/*' --filter='.bzr/*' --filter='.hg/*' --filter='.svn/*' --upstream-version=1.9 ../gif2apng-1.9.tar.gz
	gbp:info: Importing '../gif2apng-1.9.tar.gz' to branch 'upstream' (filtering out ["'CVS/*'", "'.bzr/*'", "'.hg/*'", "'.svn/*'"])...
	gbp:info: Source package is gif2apng
	gbp:info: Upstream version is 1.9
	gbp:info: Merging to 'master'
	gbp:error: Automatic merge failed.
	gbp:error: Error detected, Will roll back changes.
	gbp:info: Rolling back branch upstream by resetting it to a6733c1f1e190ac0ed4774abc3466e9986a6df5e
	gbp:info: Rolling back branch pristine-tar by resetting it to 0ee24ac614c920e30af82d602882c2ee841c88e5
	gbp:info: Rolling back tag upstream/1.9 by deleting it
	gbp:info: Rolling back branch master by resetting it to ce99782336e83a56e8e579b3cdadf93b0c19e1a8
	gbp:info: Rolling back failed merge of upstream/1.9
	gbp:error: Rolled back changes after import error.
      </programlisting>
      <para>
      In this case the import failed due to a merge conflict. Other
      reasons are running out of disk space, problems when generating
      the pristine-tar delta. If you don't want &gbp-import-orig; to
      undo changes made to the repository use
      the <option>--no-rollback</option>.
      </para>
    </sect2>
    </sect1>

    <sect1 id="gbp.import.convert">
    <title>Converting an existing &git; repository</title>
    <para>
    If the &git; repository wasn't created with &gbp-import-dsc;, you have to
    tell &gbp-buildpackage; and friends where to find the upstream sources.
    </para>
    <sect2 id="gbp.import.upstream.on.branch">
    <title>Upstream sources on a branch</title>
    <para>
    If the upstream sources are already on a separate branch, things are pretty
    simple. You can either rename that branch to the default
    <option>upstream-branch</option> name <emphasis>upstream</emphasis> with:
<programlisting>
  &gitcmd; branch -m theupstream-branch upstream
</programlisting>
    or you can tell &gbp-buildpackage; the name of the branch to use as
    <option>upstream-branch</option>:
<programlisting>
<command>cat</command> &lt;&lt;EOF &gt; <filename>.git/gbp.conf</filename>
[DEFAULT]
# this is the upstream-branch:
upstream-branch=theupstream-branch
EOF
</programlisting>
    If you then use &gbp-import-orig; to import new upstream sources, they will
    from now on end up on <emphasis>theupstream-branch</emphasis> and
    merged to the <option>debian-branch</option>.
    </para>
    </sect2>
    <sect2 id="gbp.import.upstream.not.on.branch">
    <title>Upstream sources not on a branch</title>
    <para>
    If you don't have an upstream branch but started your repository with only
    the upstream sources (not the &debian; patch), you can simply branch from that
    point. So use &gitkcmd; or &gitcmd;-log to locate the commit-id of that commit
    and create the upstream branch from there, e.g.:
<programlisting>
    &gitcmd; branch upstream $(&gitcmd; log --format='%H' | tail -1)
</programlisting>
    The important thing here is that the <envar>COMMIT_ID</envar> specifies a
    point on the master branch that carried <emphasis>only</emphasis> the
    upstream sources and not the &debian; modifications. The above example
    assumes that this was the first commit to that repository.
    </para>
    <warning><para>There's currently no <emphasis>easy</emphasis> way to create the
    <option>upstream-branch</option> if you never had the upstream sources
    as a single commit. Using &gbp-import-orig; on such repositories might lead
    to unexpected merge results.</para></warning>
    <para>In order to fix this you can prepend the upstream sources as a
    single commit to your tree using &git;'s <ulink
    url="http://git.or.cz/gitwiki/GraftPoint">grafts</ulink>. Afterwards you
    can simply create a branch as explained above and &gbp-import-orig; will
    work as expected.</para>
    <para>Alternatively, if you are only importing source from original tarballs
    (for instance when converting from a Subversion repository where the
    mergeWithUpstream was set for svn-buildpackage), you can create an empty
    upstream branch with the following commands:
<programlisting>
  <command>git checkout</command> <option>--orphan</option> <replaceable>upstream</replaceable>
  <command>git rm</command> <option>-rf</option> <replaceable>.</replaceable>
  <command>git commit</command> <option>--allow-empty</option> <option>-m</option> <replaceable>'Initial upstream branch.'</replaceable>
  <command>git checkout</command> <option>-f</option> <replaceable>master</replaceable>
  # When not using 3.0 (quilt) with the default --merge-mode=auto
  <command>git merge</command> <option>--allow-unrelated-histories</option> <replaceable>upstream</replaceable>
</programlisting>
    </para>
    </sect2>
    </sect1>

    <sect1 id="gbp.import.fromscratch">
    <title>Starting a &debian; package from scratch</title>
    <para>
    So far, we assumed you already have a &debian; package to start with, but
    what if you want to start a new package? First, create an empty repository:
    </para>
<programlisting>
  <command>mkdir</command> package-0.1
  <command>cd</command> package-0.1
  <command>git init</command>
</programlisting>
    <para>Then, you import the upstream sources, branch off the
    <option>upstream-branch</option> branch and add the &debian; files (e.g. via dh_make):
<programlisting>
  &gbp-import-orig; <option>-u</option> <replaceable>0.1</replaceable> <filename>../package-0.1.tar.gz</filename>
  <command>dh_make</command>
</programlisting>
    That's it, you're done. If you want to publish your new repository, you can use &gbp-create-remote-repo;.
    </para>
    </sect1>

    <sect1 id="gbp.import.upstream-git">
    <title>When upstream uses Git</title>
    <para>
      If upstream uses &git; for development (and you don't want to
      ignore that fact entirely), there are at least three ways to
      handle packaging. The first one uses &git; exclusively and
      creates the upstream tarballs from the upstream tag while the
      second one still uses upstream tarballs but links your packaging
      &git; history with upstreams &git; history. The third one also
      uses a tarballs but does not link to the upstream history.
    </para>

      <sect2 id="gbp.import.upstream.git.notarball">
	<title>No upstream tarballs</title>
	<para>If upstream doesn't build upstream tarballs, or you
	  don't care about them, the simplest way is to clone
	  upstream's repository and create a separate packaging branch
	  in there. You will not need &gbp-import-orig; at all with
	  this workflow. &gbp-buildpackage; will handle creating the
	  upstream tarballs needed for the Debian source package.
	</para>
	<para>
	  For that to work you need to tell &gbp; what the
	  upstream tag format looks like. Therefore you either
	  use the <option>--git-upstream-tag</option> command line option
	  or the <option>upstream-tag</option> configuration file
	  variable to specify upstream's tag format.
	</para>

	<para>
	  For example a common upstream format is to put
	  a <replaceable>v</replaceable> in front of the version
	  number.  In this case, the configuration option would look
	  like:
	</para>
<programlisting>
[DEFAULT]
upstream-tag = v%(version)s
</programlisting>
	<para>
	  <replaceable>version</replaceable> will be replaced by &gbp;
	  with the upstream version number as determined from
	  <filename>debian/changelog</filename>. The <replaceable>%()s</replaceable>
	  might be familiar from &pyformat;s. The option was placed in
	  the <emphasis>[DEFAULT]</emphasis> section instead of
	  the <emphasis>[buildpackage]</emphasis> section of the
	  configuration so other tools like &gbp-dch; make use of it
	  too.
	</para>

	<para>
	  Some upstreams use other formats though and don't separate
	  numbers by dots but rather by
	  underscore(<replaceable>_</replaceable>),
	  hyphen(<replaceable>-</replaceable>) or anything else. In
	  order to cope with that you can use version mangling of these
	  characters via substitution. The substitution works as
	  follows:
	</para>
<programlisting>
[DEFAULT]
upstream-tag = v%(version%.%_)s
</programlisting>
	<para>
	  This means that each occurrence
	  of <replaceable>.</replaceable> will be replaced
	  by <replaceable>_</replaceable> in the upstream version
	  number. For example the upstream
	  version <replaceable>1.2.3</replaceable> as determined from
	  the <filename>debian/changelog</filename> will be looked up
	  as &git; tag <replaceable>v1_2_3</replaceable> by
	  &gbp-buildpackage;.
	</para>
	<para>
	  If you want the substitution to be the <replaceable>%</replaceable> character
	  you have to escape it. E.g. <replaceable>%(version%-%\%)s</replaceable> will replace <replaceable>-</replaceable> with
	  <replaceable>%</replaceable>, transforming <replaceable>1-A.B.C</replaceable> to <replaceable>1%A.B.C</replaceable>.
	  Only a single replacement is supported and it can only replace a single character.
	  <warning>
	    <para>
	      Since some of the possible mangling characters
	      like <replaceable>_</replaceable> and <replaceable>%</replaceable> are also used to denote epochs and tilde revisions
	      these versions can't be reconstructed when mapping from &git; tags back to &debian; versions and will therefore break other tools
	      like &gbp-dch;. So use version mangling with care. It's better to come up with a Debian compatible tag format upstream.
	      See &dep14; for the currently used expansion rules for Debian version numbers.
	    </para>
	  </warning>
	</para>

	<para>If you're using &pristine-tar; you can make
	  &gbp-buildpackage; commit the generated tarball back to the
	  pristine-tar branch using
	  the <option>--git-pristine-tar-commit</option> option or you
	  can use &gbp-pristine-tar; after you've created the
	  tarballs.

	  This will make sure others building your package can exactly
	  regenerate the tarball you created when building the
	  &debian; package.
	</para>

        <sect3>
	  <title>Step by step</title>
	<para>To not make any assumptions about &gbp;'s configuration, the following steps have all options given
	  in its long versions on the command line. You can add these
	  to &gbp.conf; to save lots of typing.
	</para>

	<para>First, we clone the upstream repository. To avoid any ambiguities between the &debian; packaging repository
	  and the upstream repository, we name the upstream repository <replaceable>upstream</replaceable> instead of the
	  default <replaceable>origin</replaceable>.
<programlisting>
  <command>git clone</command> --no-checkout -o upstream git://git.example.com/libgbp.git
  <command>cd</command> libgbp
  <command>git checkout</command> -b debian/sid v1.0
</programlisting>
	  The above makes sure we have <replaceable>debian/sid</replaceable> for the &debian; packaging. We didn't create
	  any <replaceable>upstream/*</replaceable> branches; they're not needed for the packaging and only need to be
	  kept up to date. We started the branch at the commit corresponding to the tag <replaceable>v1.0</replaceable>.
      </para>

      <para>After adding the &debian; packaging, we build the package. This assumes you're using &pristine-tar;
	  and upstream uses a version number format as described above:
<programlisting>
  <command>gbp buildpackage</command> --git-pristine-tar --git-pristine-tar-commit --git-upstream-tag='v%(version)s' --git-debian-branch=debian/sid
</programlisting>
	  When updating to a new upstream version, we simply fetch from upstream and merge in the new tag. Afterwards, we
	  update the changelog and build the package:
<programlisting>
  <command>git fetch</command> upstream
  <command>git merge</command> v1.1
  <command>gbp dch</command> --debian-branch=debian/sid --snapshot --auto debian/
  &gbp-buildpackage; --git-ignore-new --git-pristine-tar --git-pristine-tar-commit --git-upstream-tag='v%(version)s'
</programlisting>
	  Note that the above &gbp-dch; call makes sure we only pickup changes in the <filename>debian/</filename>
	  directory. Since we told it to build a snapshot changelog entry and we hadn't commit the changelog yet,
	  we need to tell &gbp-buildpackage; that the working directory is unclean via the <option>--git-ignore-new</option> option.
	  Once everything looks good, commit the changelog and build a release version:
<programlisting>
  <command>gbp dch</command> --release --auto --debian-branch=debian/sid
  <command>git commit</command> -m"Release 1.1-1" debian/changelog
  &gbp-buildpackage; --git-upstream-tag='v%(version)s' --git-debian-branch=debian/sid
</programlisting>
	  If you want to share your repository with others, you can use &gbp-create-remote-repo; and &gbp-pull; as usual.
	</para>
	</sect3>
      </sect2>

      <sect2 id="gbp.import.upstream.git.tarball">
	<title>Upstream tarballs and linked upstream history</title>
	<para>If you want to track upstream's &git; but continue to import the upstream tarballs,
	  e.g. to make sure the tarball uploaded
	  to &debian; has the same checksum as upstream's, you can use the <option>--upstream-vcs-tag</option> option
	  when importing new tarballs with &gbp-import-orig;. Assuming you have the upstream source in your
	  repository with a tag <replaceable>v0.0.1</replaceable>, you can use:
<programlisting>
  &gbp-import-orig; --upstream-vcs-tag=v0.0.1 foo_0.0.1.orig.tar.gz
</programlisting>
	  to add upstream's tag as additional parent to the merge commit.
	  See <ulink url="http://bugs.debian.org/664771">#664771</ulink> for more details.
	</para>
      </sect2>

      <sect2 id="gbp.import.upstream.git.separate">
	<title>Upstream tarballs and separate upstream history</title>
	<para>
	  If you want to have upstream's &git; history available but
	  don't want to link it to your packaging history you can
	  simply keep it as a separate history. E.g. if you already have
	  a &git; repository with your packaging, change into that
	  repository and do:
<programlisting>
 &gitcmd; remote add upstream https://upstream.example.com/upstream.git
 &gitcmd; fetch upstream
</programlisting>
	  This will pull in upstream's &git; history into your repo but since
	  your packaging commits and upstreams commits have no common
	  parents the two histories will stay nicely separated.
	  Of course you can browse it and cherry-pick from it but
	  any remote repos you push to will not get upstream's history
	  by default unless you push any of upstream's refs.
	  <warning>
	    <para>
	      Since &git; has a single tag namespace pushing
	      changes with <command>git push --tags</command> will
	      push upstream's tags (and therefore it's history) too so
	      be sure to only push dedicated tag names.
	    </para>
	  </warning>
	</para>
      </sect2>

    </sect1>
    <sect1 id="gbp.branch.naming">
      <title>Branch layout</title>
      <para>
	By default, &gbp; uses one branch to keep the &debian; packaging called <emphasis>master</emphasis>
	and a branch to keep the upstream packaging called <emphasis>upstream</emphasis>.
      </para>
      <para>
	This layout is simple to get started but falls short if one needs to maintain several versions of
	the package at the same time. Therefore the following the &dep14; layout is recommended:
      </para>

      <variablelist>
	<varlistentry>
	  <term>
	    debian/&lt;release&gt;
	  </term>
	  <listitem>
	    <para>
	      the &debian; packaging for a release <emphasis>jessie</emphasis>,
	      <emphasis>stretch</emphasis>, <emphasis>sid</emphasis>, <emphasis>jessie</emphasis>, <emphasis>jessie-backports</emphasis>, <emphasis>jessie-security</emphasis>
	      or <emphasis>experimental</emphasis>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>
	    upstream/latest
	  </term>
	  <listitem>
	    <para>
	      the latest upstream sources.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>
	    dfsg/latest
	  </term>
	  <listitem>
	    <para>
	      the DFSG-clean upstream sources in case the cleanup is done via a &git;
	      merge from upstream to this branch.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>
      <para>
	In case &pristine-tar; is being used, there will be a single <emphasis>pristine-tar</emphasis>
	branch that keeps all binary deltas.
      </para>
    </sect1>
</chapter>

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