churn.sh

git log --name-only | grep php --exclude=trunk | sort | uniq -c | sort -nr | head -n 25 > churn.txt


This one looks like an odd ball but what it does is:
    - looks at the git log file, retrieving just the filenames;
    - greps to extract those filenames, excluding anything from the old SVN /trunk structure;
    - sorts the list of files to get the duplicates together;
    - eliminates the duplicates but keeps a count of them;
    - resorts the file names by that count; and
    - retrieves the top 25 entries.

It's a variant of Katrina Owen's one-liner here: https://twitter.com/kytrinyx/status/358065717179973634

You should tweak the "grep php" part to use file extensions that are relevant to your code.