chore: Expose commit hash in version module

This patch adds a marconi.version.verify_sha() convenience function,
so that continuous integration scripts can use it to verify marconi has
been installed correctly and/or to detect when the installed version is
out of date (i.e., that "import marconi" pulls in the latest version of
the library.)

Change-Id: I645c3a55a837d588fec55fa9b5c1ec579026b8f5

marconi/version.py

@@ -13,6 +13,40 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import pbr.packaging
 import pbr.version
 
 version_info = pbr.version.VersionInfo('marconi')
+
+
+def verify_sha(expected):
+    """Verifies the commit hash for an interim Marconi build.
+
+    This function may be used to verify that the version of the marconi
+    package, as imported from an environment's site-packages, is the
+    expected build. This allows continuous integration scripts to
+    detect out-of-date installations of the package.
+
+    Note that this function will ALWAYS return False for Marconi packages
+    that were not installed from git.
+
+    :param expected: The expected commit object name. May be either a full
+        or abbreviated SHA hash. If abbreviated, at least 7 digits are
+        required.
+    :returns: True if the package's version string contains a hash, and
+        that hash matches `expected`. Otherwise returns False.
+    """
+
+    # NOTE(kgriffs): Require 7 digits to avoid false positives. In practice,
+    # Git's abbreviated commit oject names will always include at least
+    # 7 digits.
+    assert len(expected) >= 7
+
+    # NOTE(kgriffs): Git usually abbreviates hashed to 7 digits, but also
+    # check 8 digits in case git decides just 7 is ambiguous. Accordingly,
+    # try the longer one first since it is more specific than the other.
+    for abbreviated in (expected[:8], expected[:7]):
+        if ('.g' + abbreviated) in version_info.release_string():
+            return True
+
+    return False

tests/unit/test_version.py

@@ -0,0 +1,39 @@
+# Copyright (c) 2013 Rackspace, Inc.
+#
+# 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.
+
+import pbr.packaging
+
+import marconi
+from marconi import tests as testing
+
+
+class TestVersion(testing.TestBase):
+
+    def test_correct_hash(self):
+        version = pbr.packaging._get_version_from_git('201X.X')
+        if version is None:
+            self.skipTest('Unable to obtain version from git')
+
+        pre, sep, commit = version.rpartition('.')
+
+        if not commit or not commit.startswith('g'):
+            self.skipTest('The git version string does not contain a hash')
+
+        sha_abbrev = commit[1:]
+        self.assertTrue(marconi.version.verify_sha(sha_abbrev))
+
+        sha_abbrev_bad = 'x' + sha_abbrev[1:]
+        self.assertFalse(marconi.version.verify_sha(sha_abbrev_bad))