Add interpolation when reading setup.cfg.

Setuptools uses the default ConfigParser object when reading
setup.cfg which does interpolation. To be consistent with that format
bumpversion must do the same.

This will close issue c4urself#21.

bumpversion/__init__.py

@@ -3,9 +3,9 @@
 from __future__ import unicode_literals
 
 try:
-    from configparser import RawConfigParser, NoOptionError
+    from configparser import RawConfigParser, ConfigParser, NoOptionError
 except ImportError:
-    from ConfigParser import RawConfigParser, NoOptionError
+    from ConfigParser import RawConfigParser, SafeConfigParser as ConfigParser, NoOptionError
 
 try:
     from StringIO import StringIO
@@ -605,13 +605,6 @@ def main(original_args=None):
     if 'current_version' in vcs_info:
         defaults['current_version'] = vcs_info['current_version']
 
-    config = RawConfigParser('')
-
-    # don't transform keys to lowercase (which would be the default)
-    config.optionxform = lambda option: option
-
-    config.add_section('bumpversion')
-
     explicit_config = hasattr(known_args, 'config_file')
 
     if explicit_config:
@@ -622,6 +615,17 @@ def main(original_args=None):
     else:
         config_file = '.bumpversion.cfg'
 
+    # setup.cfg supports interpolation - for compatibility we must do the same.
+    if os.path.basename(config_file) == 'setup.cfg':
+        config = ConfigParser('')
+    else:
+        config = RawConfigParser('')
+
+    # don't transform keys to lowercase (which would be the default)
+    config.optionxform = lambda option: option
+
+    config.add_section('bumpversion')
+
     config_file_exists = os.path.exists(config_file)
 
     part_configs = {}

tests/test_cli.py

@@ -10,6 +10,7 @@
 
 import argparse
 import subprocess
+from datetime import datetime
 from os import curdir, makedirs, chdir, environ
 from os.path import join, curdir, dirname
 from shlex import split as shlex_split
@@ -1936,6 +1937,36 @@ def test_regression_new_version_cli_in_files(tmpdir, capsys):
     assert "__version__ = '0.9.3'" == tmpdir.join("myp___init__.py").read()
     assert "current_version = 0.9.3" in tmpdir.join(".bumpversion.cfg").read()
 
+def test_correct_interpolation_for_setup_cfg_files(tmpdir, configfile):
+    '''
+    Reported here: https://github.com/c4urself/bump2version/issues/21
+    '''
+    tmpdir.chdir()
+    tmpdir.join("file.py").write("XX-XX-XXXX v. X.X.X")
+    tmpdir.chdir()
+
+    if configfile == "setup.cfg":
+        tmpdir.join(configfile).write(dedent("""
+            [bumpversion]
+            current_version = 0.7.2
+            files = file.py
+            search = XX-XX-XXXX v. X.X.X
+            replace = {now:%%m-%%d-%%Y} v. {new_version}
+            """).strip())
+    else:
+        tmpdir.join(configfile).write(dedent("""
+            [bumpversion]
+            current_version = 0.7.2
+            files = file.py
+            search = XX-XX-XXXX v. X.X.X
+            replace = {now:%m-%d-%Y} v. {new_version}
+            """).strip())
+
+    main(["major"])
+
+    assert datetime.now().strftime('%m-%d-%Y') + ' v. 1.0.0' == tmpdir.join("file.py").read()
+    assert "current_version = 1.0.0" in tmpdir.join(configfile).read()
+
 
 class TestSplitArgsInOptionalAndPositional:
     def test_all_optional(self):