Dvc

* 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

* dvc: replace flatten_dict with flatten_json (3202) efiop
* gdrive: allow configuring no_traverse (3201) efiop
* py2: remove use of `six` (3199) skshetry
* test: refactor tmp_dir/erepo_dir (3197) Suor
* external: refactor external_repo() and its users (3190) Suor
* add snap tests (2956) casperdcl

* logger: remote: use lazy formatting (3178) efiop
* pull: treat HTTP redirects without Location header as error (3169) fabiosantoscode
* api: better code documentation (3130) jorgeorpinel
* Fix import issue without remote config in the target (3120) sharidas
* completion: get --show-url (3188) mroutis
* s3: import boto3 inside _copy instead of module level (3195) mroutis
* Restyle s3: copy large objects without chunking (3187) restyled-io
* utils: resolve_output: normpath before extracting basename (3170) pared
* get: implement --show-url to display only url/path to remote (3156) skshetry
* setup: remove py2 backports (3165) mroutis
* minor comments (3173) casperdcl
* Perf improvement for file copies (3135) rxxg
* status: implement support for imported files (3150) fabiosantoscode
* conftest: remove dvc_repo, erepo, git, git_erepo (3142) pared
* point to troubleshooting guide on too many open files error (3017) pared
* major deploy tidy (3158) casperdcl
* api: identify local repos with os.path.exists (3166) mroutis
* remote: config checksum_jobs (3133) JIoJIaJIu
* Fix gdrive multiple parents file list query (3163) MaxRis
* dvc: use pydrive2 instead of pydrive (3161) efiop
* import: don't forget to set rev_lock for git files (3151) efiop
* travis: build snap in parallel with other packages (3145) efiop
* test: use helper remotes in external repro (3149) skshetry
* test: use helper remotes in child classes of TestDataCloudCLIBase (3148) skshetry
* fs: tests: remove repo_dir (3146) pared
* ssh: test: unit, utils: test: unit: remove repo_dir (3147) pared
* connection: test: unit: remove repo_dir (3143) pared
* test: use helper remotes in TestCases (3136) skshetry
* tests: repro: unit: migrate to dir helpers (3138) pared
* tests: run: unit: migrate to dir helpers (3139) pared
* update: tests: unit: migrate to dir helpers (3141) pared
* stage: tests: unit: migrate to dir helpers (3140) pared
* tests: local: unit: migrate to dir helpers (3137) pared
* metrics: introduce `diff` (3051) efiop

* Fix build issues.

* test: scm: convert to dir helpers (3116) efiop
* get: refactor handling of git files and git-only repos (3114) efiop
* test: get_url: convert to dir helpers (3115) efiop
* test: init: convert to dir helpers (3117) efiop
* tests: external_repo: convert to dir helpers (3118) efiop
* add space for import help text (3126) pared
* test: refactor ssh related functions in test helper classes (3123) skshetry
* summon: fixes and dvcx prereq (3101) Suor
* gdrive: add support for teamDriveId (3016) efiop
* rwlock: flush and fsync (3076) efiop
* get: handle non-DVC repositories (3097) fabiosantoscode
* run: tests: migrate to dir helpers (3094) pared
* state: tests: migrate to dir helpers (3096) pared
* update: tests: migrate to dir helpers (3100) pared
* stage: tests: migrate to dir helpers (3099) pared
* tests: remove redundant native ssh tests (3104) efiop
* py3: use links from os module (3090) mroutis
* repro: tests: migrate to dir helpers (3091) pared
* dvc: optimize Git.is_tracked() (3053) Suor
* Move fs utilities to fs.py from __init__.py (3093) algomaster99
* import url: test: migrate to dir helpers (3072) pared
* output: tests: migrate to dir helpers (3083) pared
* py3: remove code related to py2 limitations (3034) mroutis
* remote: test: migrate to dir helpers (3086) pared
* pipeline: test: migrate to dir helpers (3085) pared
* install: tests: migrate to dir helpers (3074) pared
* setup: get rid of py2 reqs (3082) efiop
* py3: use format_exc instead of print_exception (3078) mroutis
* rwlock: check that .dvc/lock is locked (3075) efiop
* ui: warn about ignored options for `dvc status` and a grammar fix (3027) Suor
* ui: don't show exception for "Too many files" error (3058) efiop
* Write test for `walk_files` to check if it accepts Path-like and str objects (3035) algomaster99
* fix snap deploy stage (3064) casperdcl
* dvc: update gc to remove unpacked dir (3054) sharidas
* test: merge _should_test_aws and _get_aws_url inside S3 test helper (3073) skshetry
* test: merge _should_test_oss and _get_oss_url inside OSS test helper (3071) skshetry
* http/ imp tests - migrate do dir helpers (3070) pared
* dependency: test: migrate to dir helpers (3068) pared
* cache: test: migrate to dir helpers (3067) pared
* analytics: tests: migrate to dir helpers (3066) pared
* tests: api: convert to dir helpers (3044) pared
* Snap classic deployment (3063) casperdcl
* completion: fix --relink problem (3061) mroutis
* local-related methods should verify that WorkingTree is in use (3018) pared
* tests: remote: local: migrate to dir fixtures (3049) pared
* import: allow importing from non-DVC git repositories (3020) chatcannon
* test: Merge _should_test_azure and _get_azure_url inside Azure test helper (3055) skshetry
* test: add _should_test_gdrive and _get_gdrive_url inside GDrive (3056) skshetry
* py3: use yield from where appropriate (3052) Suor
* test: do not bootstrap repo template and version files in erepo_dir (3045) Suor
* dvc: optimize and clean up stages collection (3048) Suor
* dvc: autowrap repo tree into CleanTree (3047) Suor
* test: add TmpDir.chdir() (3043) Suor
* dvc: clean brancher (3046) Suor
* py3: refactor exceptions (3042) mroutis
* py3: use new magic from PEP 3135 (3039) mroutis
* Restyle fix for base None value (3041) restyled-io
* Ensure `relpath` accepts str and Path-like objects (3037) algomaster99
* metrics: don't show working tree if it is clean (3025) Suor
* ui: add checkout --relink to autocomplete scripts (3026) Suor
* py3: migrate utils/compat.py to compat.py (3032) mroutis
* py3: remove imports from utils.compat (3031) mroutis
* py3: remove csv_reader and makedirs from utils/compat.py (3030) mroutis
* py3: remove methods for casting bytes in python 2 (3029) mroutis