Issue 5250 - Add copyright update script

update-copyright/README.md

+# update-copyright
+
+This script accepts a URL to a mercurial index as input. It then:
+* makes a local copy of each repo
+* updates the copyright information on every file to the current year
+* attempts to push the updates
+
+If a user doesn't have permission to push to a repo, the script will make a
+local `repo-name.patch` file to submit later. 
+
+You are free to use this for other projects but please keep in mind that we
+make no stability guarantees whatsoever and might change functionality any
+time.
+
+## How to use
+
+To update the copyright on all the repos indexed at
+[https://hg.adblockplus.org/](https://hg.adblockplus.org/), you can use the
+accompanying shell script, e.g.:
+
+    ./run_update_copyright.sh
+
+To run the script elsewhere, you must specify the URL for a Mercurial index
+site to scrape, e.g.:
+
+    ./update_copyright.py -u https://hg.example.com/
+
+You may also specify a base URL of a remote repo to push to, if it is
+different than the base URL of the index page, e.g.:
+
+    ./update_copyright.py -u https://hg.example.com/ -p ssh://user@hg.
+    example.com/
+
+## Testing
+
+Testing can be run via [tox](http://tox.readthedocs.org/).