source helpers from `git squash`
Merge pull request #48 from ryan-williams/squash

source helpers from `git squash`
add `git ls-hashes` command for all files’ shasums
add `git all-hashes` to list all commit hashes
only list top levels of untracked directories
add some “git -—no-pager diff” aliases
Fix git-conflicting-checkout-theirs-continue