Place repository in root directory of any Magento installation, or just copy integrity.php and consistency.php into the /shell directory. Use "php -f integrity.php -- help" and "php -f consistency.php -- --help" to see a full list of options in the shell.
The Magento Integrity Scanner is a tool to help find overwrites, rewrites, and other changes to a Magento installation that may cause issues. It is a tool to help debug and easily identify problem spots in a given install.
If you're having issues running it, try replacing shell/abstract.php with a fresh copy from Magento's latest community version.
The current version only scans for rewritten blocks and models, as well as Mage files being overridden in app/code/local and a summated list of installed extensions. Future versions will scan for rewritten controllers as well.
The Core Consistency Check script builds a report of how your install of Magento compares to a clean install of the same version. Use --help to see the default parameters of the scan. It is required that you download a clean install of Magento and place it somewhere for the script to diff against. A report of all difference counts and files will be built, as well as a collection of files representing the differences found.