add git churn command

git/.gitconfig

@@ -235,6 +235,56 @@
     unignore = update-index --no-assume-unchanged
     ignored = !git ls-files -v | grep "^[[:lower:]]"
 
+    # churn: show log of files that have many changes
+    #
+    #   * Written by (Corey Haines)[http://coreyhaines.com/]
+    #   * Scriptified by Gary Bernhardt
+    #   * Obtained from https://github.com/garybernhardt/dotfiles/blob/master/bin/git-churn
+    #   * Edited for sixarm_git_config repo by Joel Parker Henderson
+    #   * Comments by Mislav http://mislav.uniqpath.com/2014/02/hidden-documentation/
+    #
+    # Show churn for whole repo:
+    #
+    #   $ git churn
+    #
+    # Show churn for specific directories:
+    #
+    #   $ git churn app lib
+    #
+    # Show churn for a time range:
+    #
+    #   $ git churn --since='1 month ago'
+    #
+    # These are all standard arguments to `git log`.
+    #
+    # It's possible to get valuable insight from history of a project not only
+    # by viewing individual commits, but by analyzing sets of changes as a whole.
+    # For instance, git-log-churn compiles stats about which files change the most.
+    #
+    # For example, to see where work on an app was focused on in the past month:
+    #
+    #     $ git churn --since='1 month ago' app/ | tail
+    #
+    # This can also highlight potential problems with technical debt in a project.
+    # A specific file changing too often is generally a red flag, since it probably
+    # means the file either needed to be frequently fixed for bugs, or the file
+    # holds too much responsibility and should be split into smaller units.
+    #
+    # Similar methods of history analysis can be employed to see which people were
+    # responsible recently for development of a certain part of the codebase.
+    #
+    # For instance, to see who contributed most to the API part of an application:
+    #
+    #    $ git log --format='%an' --since='1 month ago' app/controllers/api/ | \
+    #      sort | uniq -c | sort -rn | head
+    #
+    #    109 Alice Anderson
+    #    13 Bob Brown
+    #    7 Carol Clark
+    #
+    churn = !git log --all --find-copies --find-renames --name-only --format='format:' "$@" | sort | grep -v '^$' | uniq -c | sort | awk 'BEGIN {print "count\tfile"} {print $1 "\t" $2}' | sort -g
+
+
 # URL shorthands
 
 [url "ssh://[email protected]/"]