add a way of keeping deps in sync

elm_deps_sync.py

@@ -0,0 +1,68 @@
+#! /usr/bin/env python
+from __future__ import print_function
+
+import sys
+import json
+import argparse
+
+
+def sync_versions(top_level_file, spec_file, quiet=False, dry=False):
+    """ first file should be the top level elm-package.json
+        second file should be the spec file
+    """
+
+    with open(top_level_file) as f:
+        top_level = json.load(f)
+
+    with open(spec_file) as f:
+        spec = json.load(f)
+
+    messages = []
+
+    for (package_name, package_version) in top_level['dependencies'].items():
+        if package_name not in spec['dependencies']:
+            spec['dependencies'][package_name] = package_version
+
+            messages.append('Package {package_name} inserted to {spec_file} for the first time at version "{package_version}"'.format(
+                package_name=package_name, spec_file=spec_file, package_version=package_version)
+            )
+        elif spec['dependencies'][package_name] != package_version:
+            spec['dependencies'][package_name] = package_version
+
+            messages.append('Changing {package_name} from version {package_version} to {other_package_version}'.format(
+                    package_version=package_version, package_name=package_name,
+                    other_package_version=spec['dependencies'][package_name])
+                )
+
+    if len(messages) > 0:
+        print('{number} files changed.'.format(number=len(messages)))
+
+        if not dry:
+            with open(spec_file, 'w') as f:
+                f.write(json.dumps(spec))
+        else:
+            print("No changes written.")
+
+        if not quiet:
+            print('\n'.join(messages))
+    else:
+        print('No changes needed.')
+
+
+def main():
+
+    parser = argparse.ArgumentParser(description='Sync deps between a parent and a sub')
+
+    parser.add_argument('--quiet', '-q', action='store_true', help='don\'t print anything', default=False)
+    parser.add_argument('--dry', '-d', action='store_true', help='only print possible changes', default=False)
+
+
+    parser.add_argument('top_level_file')
+    parser.add_argument('spec_file')
+    args = parser.parse_args()
+
+    sync_versions(args.top_level_file, args.spec_file, quiet=args.quiet, dry=args.dry)
+
+
+if __name__ == '__main__':
+    main()