* experiments: move executor into a module
* experiments: separate executor into base/local
* rename LocalExecutor to TempDirExecutor, run in .dvc/tmp by default
* git: restore HEAD using reset not checkout in detached_head()
* experiments: support calling BaseExecutor.reproduce directly for
workspace runs
* experiments: run single experiments in local workspace by default
* update experiments tests for workspace changes
* experiments: update checkpoints for workspace runs
* update checkpoints tests
* update test_show
* add force param for apply
* exp apply: add --force option
* exp run/res: add --temp option to force tempdir execution for single
experiments
* force apply in non-apply specific tests
* experiments: commit to refs/exps/... instead of branch heads
* update exp show
* restore checkpoint_resume kwarg
* refactor new() to use experiments stash
* experiments: use refspecs to populate and collect executors
* experiments: use new stash and merge on exp checkout
* experiments: fix executor chdir
* experiments: update run and show
* skip checkout after reproduce
* checkpoints: use experiments refspecs
* check if workspace was stashed before applying
* exp show: unify checkpoint/standalone experiment collection
* git: move iter_refs to backend
* update for scm changes
* experiments: replace exp checkout in favor of exp apply
* git: handle rev_parse errors in resolve_commit
* update refs containing and baseline check
* fix sigint handling for checkpoints
* update checkpoint exists behavior
* fix checkpoint baseline behavior
* update tests
* experiments: update gc
* update show tests
* fix type checking errors
* update diff
* scm: add diff, describe
* experiments: generate human readable names
* exp run/resume: allow user specified exp name with -n/--name
* update tests
* experiments: add `exp branch` for promoting experiment to full branch
* fix test
* fix missing file
* experiments: explicitly close scm instances before cleaning up tmp dir
Peter Rowlands (변기호)