Cherry picks with modifications from Ozkan's jdsu-ger branch.

Updates include

    Added support for wildcards in .gitattributes

    Added file name display in verbose mode during clean & smudge operations

    Fix handling of empty files in filter clean/smudge functions

    Creation of a "share" directory which allows for fine-grained
        push/pull and better disk utilization.

    Addition of pre-push,pre-rebase, and post-merge hooks to allow
        git push/pull to automatically call git fat push/pull commands as needed

    Added a help command

    test.sh and test-retroactive.sh scripts pass.