Dvc

* dvc: do not check for isdir on recursive out collect (3268) Suor
* lint:beautysh pre-commit hook (3263) casperdcl
* api: prepare for dvcx summon/publish (3251) Suor
* diff: reimplement interface and tests from scratch (3229) mroutis

* install: fix post-checkout hook (3253) efiop

* gdrive: Init drive if corpora property value requested. (3252) MaxRis
* UI progress cleanup (2846) casperdcl

* Set corpora and driveId params values based on type of remote disk - shared or user's. (3239) MaxRis
* config: verify before saving a modification (3193) mroutis
* erepo: make it better (3234) Suor

* push: improve 'no remote specified' hint (3213) fabiosantoscode
* Remove usage of google-api-python-client deps (3232) MaxRis
* install: post-checkout: run only on branches/tags (3228) efiop
* remote: verify cache exists on dir checksum (3225) pared
* some doc link fixes (3231) pared
* erepo: pull each time (3227) Suor

* import-url: test: prevent in-repo testing (3224) pared
* Update Google Project credentials to run tests (3216) MaxRis
* api: fallback to external_repo if not a DVC repository (3222) skshetry
* dvc: add sanity checks for hard/symlinks (3088) efiop
* tests: replace spy() with pytest-mock spy (3208) fabiosantoscode
* hooks: checkout: fix incorrect dvc repo detection (3223) efiop
* get: copy edits aroud --show-url, "dvc", et al. (3220) jorgeorpinel
* get/imp: update help output descriptions (3214) jorgeorpinel
* another attempt at travis dpl snap (3212) casperdcl
* brancher: do not get tree if there's no revs (3211) skshetry
* fetch: trust remote checksums (3200) pared
* fix snap stable & edge release errors (3209) casperdcl
* test: add git_dir (3206) Suor
* erepo: fix DependencyREPO schema (3204) efiop
* exception: fix spelling (3205) skshetry