sync: make sync usable from outside ohmu_common_py directory

And don't resync files with no changes plus log what we do.

sync.py

@@ -5,6 +5,7 @@
 See LICENSE for details
 """
 
+import logging
 import os
 import version
 import sys
@@ -19,17 +20,42 @@
 ]
 
 
-def main(target):
-    ver = version.get_project_version("ohmu_common_py/version.py")
-    curdir = os.path.dirname(__file__)
+def sync_files(source_dir, target_name, target_dir=None, common_dir=None, test_dir=None):
+    ver = version.get_project_version(os.path.join(os.path.dirname(__file__), "ohmu_common_py/version.py"))
     for src_f in FILES:
-        with open(os.path.join(curdir, src_f), "r") as fp:
+        with open(os.path.join(source_dir, src_f), "r") as fp:
             source = fp.read()
-        dst_f = src_f.replace("ohmu_common_py", target)
-        dst = os.path.join(curdir, "..", target, dst_f)
+        source = source.replace("ohmu_common_py", target_name)
+        if target_dir:
+            dst = os.path.join(target_dir, src_f.replace("ohmu_common_py", target_name))
+        elif src_f.startswith("ohmu_common_py/") and common_dir:
+            dst = os.path.join(common_dir, src_f.replace("ohmu_common_py/", ""))
+        elif src_f.startswith("test/") and test_dir:
+            dst = os.path.join(test_dir, src_f.replace("test/", ""))
+        else:
+            logging.info("%r: skipping", src_f)
+            continue
+
+        # check existing file for changes
+        if os.path.exists(dst):
+            with open(dst, "r") as fp:
+                existing_data = fp.read()
+            existing_data = "\n".join(existing_data.splitlines()[1:]) + "\n"
+            if existing_data == source:
+                logging.info("%r: no update required", dst)
+                continue
         with open(dst, "w") as fp:
             fp.write("# Copied from https://github.com/ohmu/ohmu_common_py {} version {}\n".format(src_f, ver))
-            fp.write(source.replace("ohmu_common_py", target))
+            fp.write(source)
+            logging.info("%r: UPDATED", dst)
+
+
+def main(target):
+    from ohmu_common_py import logutil
+    logutil.configure_logging()
+    curdir = os.path.dirname(__file__)
+    target_dir = os.path.join(curdir, "..", target)
+    sync_files(source_dir=curdir, target_name=target, target_dir=target_dir)
 
 
 if __name__ == "__main__":