Dvc

* dvc: use ' to mark dynamic command output, et al. (2986) jorgeorpinel
* tests: use dir_helpers on repo (2950) mroutis
* tests: use dir helpers on updater (2952) mroutis
* import: test: refactor to dir helpers (2935) pared
* ui: reorder checkout options to go from common to rare (2966) Suor
* remote: s3: adjust jobs number basing on file descriptors number (2866) pared
* import: allow downloading regular files/dirs tracked by git (2889) Baranowski
* Standardize gdrive tests with others remotes (2958) MaxRis
* temporary_windows_drive fixture: move to dir_helpers (2937) pared
* tests: use dir helpers on analytics (2951) mroutis

* Restyle remote: use absolute from root for gdrive credentials file (2949) e3bo

* remote: make `copy` links atomic for local/hdfs/ssh (2943) efiop
* dvc: add checkout --relink (2922) Suor

* remote: Extend S3 remote support for custom ACL (2931) rbvesb

* dvc: release locks when running a command (2584) efiop
* run: provide a hint if we get output duplication error (2941) efiop

* dvc: make flufl.lock opt-in and use zc.lockfile (2918) efiop
* test: a couple of dir helpers fixes (2938) Suor
* checkout: test: refactor to dir helpers (2934) pared
* commit: test: refactor to dir helpers (2932) pared
* snap: remove plugs (incompatible with classic) (2939) casperdcl
* use cache dir as a default remote when importing from local repo (2915) maykulkarni
* import-url: add directories to examples (2907) efiop
* test: move: convert to dir helpers (2926) pared