[WIP] pre 2.0 command description sync (vs. docs)

[jorgeorpinel]

Rel:

• https://dvc.org/doc/command-reference
• more 1.x updates... (import) dvc.org#2094 (review)
• TO-DO: matching docs PR (WIP)
• Consistent const. names and formatting around my code edits

• ❗ I have followed the Contributing to DVC checklist.

• 📖 If this PR requires documentation updates, I have created a separate PR (or issue, at least) in dvc.org and linked it here.

Thank you for the contribution - we'll try to review it as soon as possible. 🙏

[jorgeorpinel]

BTW, I can't run the lint check locally. I get an error at mypy. Anyone else has that problem?

mypy.....................................................................Failed
- hook id: mypy
- exit code: 1

dvc/scm/git/backend/dulwich.py: note: In member "commit" of class "DulwichBackend":
dvc/scm/git/backend/dulwich.py:158:13: error:
Unexpected
keyword
argument
"no_verify"
for
"commit"

[call-arg]
                commit(self.root_dir, message...
                ^
Found 1 error in 1 file (checked 228 source files)

I'm Windows Terminal on WSL 2 / Ubuntu 18

[jorgeorpinel]

Sorry, didn't mean to abandon this. Will close for now...