Add new normalize utility

Purpose: cleanup requirements.txt in order to be more readable

Implemented features:
- comments are preceded by two spaces and separated from '#' by one space (PEP8 style)
- specificiers are ordered

Change-Id: Ic9a4c044b2740b1d0167c237b67822a9794356c8

cmds/normalize

@@ -0,0 +1,83 @@
+#! /usr/bin/env python
+
+# 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 argparse
+from distutils.version import LooseVersion
+
+import pkg_resources
+
+
+def cmp_specifier(a, b):
+    weight = {'>=': 0, '>': 0,
+              '==': 1 , '~=': 1, '!=': 1,
+              '<': 2., '<=': 2}
+    wa, wb = weight[a[0]], weight[b[0]]
+    res = cmp(wa, wb)
+    if res != 0:
+        return res
+    else:
+        return cmp(LooseVersion(a[1]), LooseVersion(b[1]))
+
+
+def lint(requirements):
+    output = []
+    for line in requirements:
+        # comments and empty lines are untouched
+        if line.startswith("#") or line == "":
+            output.append(line)
+            continue
+
+        # split comments
+        parts = line.split('#', 1)
+        if len(parts) > 1:
+            base, comments = parts
+        else:
+            base, comments = parts[0], ""
+            base, comments = base.strip(), comments.strip()
+        # split extras specifiers
+        parts = base.split(';', 1)
+        if len(parts) > 1:
+            base, extras = parts
+        else:
+            base, extras = parts[0], ""
+        base, extras = base.strip(), extras.strip()
+
+        req = pkg_resources.Requirement.parse(base)
+        name = req.key
+        # FIXME: not py3 compliant
+        specs = ["%s%s" % x for x in sorted(req.specs, cmp=cmp_specifier)]
+        name += ','.join(specs)
+        if extras != "":
+            name += ";%s" % extras
+        if comments != "":
+            name += "  #%s" % comments
+        output.append(name)
+    return output
+
+        
+def main():
+    parser = argparse.ArgumentParser(description="Normalize requirements files")
+    parser.add_argument('requirements',
+                        help=['requirements file input'])
+    args = parser.parse_args()
+    with open(args.requirements) as f:
+        requirements = [line.strip() for line in f.readlines()]
+    
+    for line in lint(requirements):
+        print(line)
+
+
+if __name__ == '__main__':
+    main()