Add option to create release note from user-provided template

This is useful when automating the release note creation (when
automating commit creation).

Change-Id: I11793aaa3232b0f2c44521a998d466f427eecd93

doc/source/user/usage.rst

@@ -40,6 +40,20 @@ The ``--edit`` option opens the new note in a text editor.
     ... Opens the editor set in the EDITOR environment variable, editing the new file ...
     Created new notes file in releasenotes/notes/slug-goes-here-95915aaedd3c48d8.yaml
 
+The ``--from-template`` option allows you to use a pre-defined file and use
+that as the release note.
+
+::
+
+    $ reno new slug-goes-here --from-template my-file.yaml
+    ... Creates a release note using the provided file my-file.yaml ...
+    Created new notes file in releasenotes/notes/slug-goes-here-95915aaedd3c48d8.yaml
+
+.. note::
+
+    You can also combine the flags ``--edit`` and ``--from-template``
+    to create a release note from a specified file and immediately start an
+    editor to modify the new file.
 
 By default, the new note is created under ``./releasenotes/notes``.
 The ``--rel-notes-dir`` command-line flag changes the parent directory

releasenotes/notes/Enable-using-tempalte-file-be734d8698309409.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    The --from-template flag was added to the release note creation command.
+    This enables one to create a release note from a pre-defined template,
+    which is useful when automating the creation of commits.

reno/create.py

@@ -47,6 +47,16 @@ def _edit_file(filename):
     return True
 
 
+def _get_user_template(template_file):
+    if not os.path.exists(template_file):
+        raise ValueError(
+            'The provided template file %s doesn\'t '
+            'exist' % template_file,
+        )
+    with open(template_file, 'r') as f:
+        return f.read()
+
+
 def create_cmd(args, conf):
     "Create a new release note file from the template."
     # NOTE(dhellmann): There is a short race window where we might try
@@ -57,7 +67,11 @@ def create_cmd(args, conf):
     # concern.
     slug = args.slug.replace(' ', '-')
     filename = _pick_note_file_name(conf.notespath, slug)
-    _make_note_file(filename, conf.template)
+    if args.from_template:
+        template = _get_user_template(args.from_template)
+    else:
+        template = conf.template
+    _make_note_file(filename, template)
     if args.edit and not _edit_file(filename):
         print('Was unable to edit the new note. EDITOR environment variable '
               'is missing!')

reno/main.py

@@ -99,6 +99,10 @@ def main(argv=sys.argv[1:]):
         action='store_true',
         help='Edit note after its creation (require EDITOR env variable)',
     )
+    do_new.add_argument(
+        '--from-template',
+        help='Template to get the release note from.',
+    )
     do_new.add_argument(
         'slug',
         help='descriptive title of note (keep it short)',

reno/tests/test_create.py

@@ -13,6 +13,7 @@
 # under the License.
 
 import fixtures
+import io
 import mock
 
 from reno import create
@@ -45,6 +46,16 @@ class TestCreate(base.TestCase):
         super(TestCreate, self).setUp()
         self.tmpdir = self.useFixture(fixtures.TempDir()).path
 
+    def _create_user_template(self, contents):
+        filename = create._pick_note_file_name(self.tmpdir, 'usertemplate')
+        with open(filename, 'w') as f:
+            f.write(contents)
+        return filename
+
+    def _get_file_path_from_output(self, output):
+        # Get the last consecutive word from the output and remove the newline
+        return output[output.rfind(" ") + 1:-1]
+
     def test_create_from_template(self):
         filename = create._pick_note_file_name(self.tmpdir, 'theslug')
         create._make_note_file(filename, 'i-am-a-template')
@@ -52,6 +63,29 @@ class TestCreate(base.TestCase):
             body = f.read()
         self.assertEqual('i-am-a-template', body)
 
+    def test_create_from_user_template(self):
+        args = mock.Mock()
+        args.from_template = self._create_user_template('i-am-a-user-template')
+        args.slug = 'theslug'
+        args.edit = False
+        conf = mock.Mock()
+        conf.notespath = self.tmpdir
+        with mock.patch('sys.stdout', new=io.StringIO()) as fake_out:
+            create.create_cmd(args, conf)
+        filename = self._get_file_path_from_output(fake_out.getvalue())
+        with open(filename, 'r') as f:
+            body = f.read()
+        self.assertEqual('i-am-a-user-template', body)
+
+    def test_create_from_user_template_fails_because_unexistent_file(self):
+        args = mock.Mock()
+        args.from_template = 'some-unexistent-file.yaml'
+        args.slug = 'theslug'
+        args.edit = False
+        conf = mock.Mock()
+        conf.notespath = self.tmpdir
+        self.assertRaises(ValueError, create.create_cmd, args, conf)
+
     def test_edit(self):
         self.useFixture(fixtures.EnvironmentVariable('EDITOR', 'myeditor'))
         with mock.patch('subprocess.call') as call_mock: