Merge pull request #23 from ryan-williams/copy-diffs

refactor copy-diffs, more tests and fixes
Merge pull request #22 from ryan-williams/comments

Comments, documentation, cleanup
fix safe-push-force usage of uncommitted script
fix clean_branches

add/use reverse-chron opt local-branches
export GIT_HELPERS_HOME, use it for `source`ing

fixes #27
source helpers in `clean_branches`, for `count` fn
add and use `prompt` helper

fixes #25, provides missing `clean_branches` dependency
more verbose error message in tests’ `check_link`
fix clean_branches shebang line
Merge pull request #28 from ryan-williams/home

fix `source`ing, add `prompt` helper
specify that arg to `git-lg` is a branch, not file

fixes #30
clean up, add alias for git-delete-merged-branches
add success message to end of run-tests script
trap EXIT, clean up test files in test scripts

fixes #32
Merge pull request #31 from ryan-williams/lg

specify that arg to `git-lg` is a branch, not file
Merge pull request #33 from ryan-williams/trap

trap EXIT, clean up test files in test scripts
set GIT_HELPERS_HOME in mk-git-test

allows this test to run correctly from an alternate copy of the
git-helpers repo, other than the one at $GIT_HELPERS_HOME.
add comment and extra checks to mk-git-test
fix overwrite-prompt logic in `mk-git`, add test
fix-broken-links: error when 0 candidates found

also don't accept self as a candidate for link-fixing

fixes #37