Check valid import branch argument value

Report invalid import branch to user when combined with --finish option
as the value provided to --import-branch must be a valid reference.

Change-Id: Ibd9e52bd4e387e997cb845721e49a91520989298
Closes-Bug: #1625878

git_upstream/commands/import.py

@@ -140,6 +140,13 @@ class ImportCommand(LogDedentMixin, GitUpstreamCommand):
             import_branch=self.args.import_branch,
             extra_branches=self.args.branches)
 
+        # perform additional checks requiring git operations
+        if self.args.finish and not import_upstream.is_valid_commit(
+                self.args.import_branch):
+            self.parser.error(
+                "Invalid ref for argument '--import-branch', '%s' not found!"
+                % self.args.import_branch)
+
         self.log.notice("Searching for previous import")
         strategy = ImportStrategiesFactory.create_strategy(
             self.args.strategy, branch=self.args.branch,

git_upstream/tests/commands/import/test_failure.py

@@ -0,0 +1,75 @@
+# Copyright (c) 2016 Hewlett Packard Enterprise Company, L.P.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for the 'import' command failures"""
+
+import inspect
+import os
+
+import mock
+from six import moves
+from testtools import matchers
+
+from git_upstream import main
+from git_upstream.tests import base
+
+
+class TestImportCommandFailure(base.BaseTestCase):
+
+    tree = [
+        ["A", []],
+        ["B", ["A"]],
+        ["C", ["B"]],
+        ["D", ["C"]],
+        ["E", ["B"]],
+        ["F", ["E"]]
+    ]
+
+    branches = {
+        'head': ["master", "D"],
+        'upstream': ["upstream/master", "F"]
+    }
+
+    def setUp(self):
+        self.commands, self.parser = main.build_parsers()
+
+        script_cmdline = self.parser.get_default('script_cmdline')
+        script_cmdline[-1] = os.path.join(os.getcwd(), main.__file__)
+        self.parser.set_defaults(script_cmdline=script_cmdline)
+
+        # builds the tree to be tested
+        super(TestImportCommandFailure, self).setUp()
+
+        self.upstream_branch = self.branches['upstream'][0]
+        self.target_branch = self.branches['head'][0]
+
+    def test_invalid_import_branch(self):
+        """Test that a parser error is returned on an invalid import branch
+
+        Checks that if an invalid import branch is passed as an argument
+        when trying to use the --finish mode that the command will exit
+        with a parser error.
+        """
+        self.git.tag(inspect.currentframe().f_code.co_name,
+                     self.upstream_branch)
+
+        args = self.parser.parse_args(
+            ['import', '--finish', '--import-branch', 'invalid',
+             'upstream/master'])
+        with mock.patch('sys.stderr', new_callable=moves.StringIO) as console:
+            self.assertRaises(SystemExit, args.cmd.run, args)
+            self.assertThat(
+                console.getvalue(),
+                matchers.Contains("'invalid' not found!"))