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
make `git-links` respect directory arguments
make `command-exists` see aliases; add test
add simplify() path helper
better relpath handling of intermediate “..”s
Merge pull request #45 from ryan-williams/utils

add a few utilities for listing files / commits