buildpackage: Include uncommitted changes with --git-ignore-new and export-dir

docs/chapters/building.xml

@@ -58,6 +58,11 @@
     state of the current index, which can be used to include staged but uncommitted
     changes in the build. Whereas the special argument
     <replaceable>WC</replaceable> exports the current working copy as is.</para>
+    <para>By default uncommitted changes are not exported and
+    &gbp-buildpackage; aborts when it finds them. Passing
+    <option>--git-ignore-new</option> includes the uncommitted changes (both
+    modified and untracked files) in the exported tree, mirroring the behaviour
+    of building without <option>--git-export-dir</option>.</para>
     <para>If you want to default to build in a separate build area, you can
     specify the directory to use in the <filename>gbp.conf</filename> file.
 <programlisting>

docs/manpages/gbp-buildpackage.xml

@@ -758,7 +758,11 @@
             <para>
               Don't abort if there are uncommitted changes in the source tree or
               the current branch doesn't match the
-              <replaceable>DEBIAN-BRANCH</replaceable>.
+              <replaceable>DEBIAN-BRANCH</replaceable>. The uncommitted changes
+              are included in the build. This holds whether or not
+              <option>--git-export-dir</option> is used, as long as
+              <option>--git-export</option> is left at its default
+              (<replaceable>HEAD</replaceable>).
             </para>
           </listitem>
 	</varlistentry>

gbp/scripts/buildpackage.py

@@ -62,6 +62,13 @@ def maybe_write_tree(repo: DebianGitRepository, options: optparse.Values) -> str
             tree = repo.write_tree()
         elif options.export == wc_name:
             tree = write_wc(repo)
+        elif options.ignore_new and options.export == 'HEAD':
+            # --git-ignore-new asks to build with the uncommitted changes
+            # in the source tree. Without an export-dir we build in the
+            # working copy and the changes are included, so export the
+            # working copy here too to keep the behaviour consistent
+            # (#1091531).
+            tree = write_wc(repo)
         else:
             tree = options.export
         if not repo.has_treeish(tree):

tests/component/deb/test_buildpackage.py

@@ -222,6 +222,37 @@ def test_export_wc_buildpackage(self, repo):
         self._test_buildpackage(repo, ["--git-export=WC", "--git-export-dir=../foo/bar"])
         assert os.path.exists("../foo/bar")
 
+    @RepoFixtures.quilt30()
+    def test_export_dir_ignore_new(self, repo):
+        """
+        Test that --git-ignore-new includes uncommitted changes in the export
+        when an export dir is used (#1091531).
+
+        Without an export dir the package is built in-place in the working copy
+        so uncommitted changes are always part of the build. With an export dir
+        the tree to export defaults to HEAD, which used to silently drop those
+        changes. Before the fix both assertions below failed because HEAD was
+        exported instead of the working copy.
+        """
+        # Uncommitted modification to a tracked file ...
+        rules = os.path.join(repo.path, 'debian', 'rules')
+        with open(rules, 'a') as f:
+            f.write('\n# uncommitted-marker\n')
+        # ... and an untracked new file
+        with open(os.path.join(repo.path, 'untracked.txt'), 'w') as f:
+            f.write('untracked')
+
+        self._test_buildpackage(repo, ['--git-ignore-new',
+                                       '--git-no-purge',
+                                       '--git-export-dir=../bdir'])
+
+        exported = '../bdir/hello-debhelper-2.8'
+        with open(os.path.join(exported, 'debian', 'rules')) as f:
+            assert '# uncommitted-marker' in f.read(), \
+                "Uncommitted change to tracked file was not exported"
+        assert os.path.exists(os.path.join(exported, 'untracked.txt')), \
+            "Untracked file was not exported"
+
     @RepoFixtures.native()
     def test_argument_quoting(self, repo):
         """Test that we quote arguments to builder (#850869)"""