* test: remove never used copy of load_stage_file()
* dvc: save comments and custom formatting in stage files
* Add a couple of TODOs
* test: test repro doesn't clear comments and formatting in .dvc
As part of this I started writing pytest-like tests and added commonly
used fixtures.
* test: simplify and prettify dvc formatting retained test
Also test that line comments after md5 fields are retained.
* test: fix tests
* dvc: fix stage and metrics opens not closed
* dvc: always use utf-8 in stage files
It used to encode in system default encoding. Not sure if PyYAML was
handling this silently or we were just lucky all the way.
* test: unit test apply_diff()
* test: remove TODOs and ASK
* dvc: polish dvc-formatting PR
* dvc: move stage load/dump utils to a new stage utils file
* dvc: clean up apply_diff()
* test: test stage md5 ignores comments
* test: remove pytests starting marker
pared
Alexander Schepanovski
vyloy
Ruslan Kuprieiev