dvc-git command pairs

[casperdcl]

Probably a duplicate but:

1. make a list of dvc & git commands which are often run together, e.g.

• git checkout <ID> && dvc checkout
• dvc add <file> && git add .gitignore <file>.dvc

2. discuss ways to make running such command pairs easier

• (easy) alias certain commands (not really command pairs)
  • git config --global alias.run '!dvc run' && complete -F git-run _dvc_run
• (hard) dvc will also run git commands?
  • dvc --git/gdvc/dvcg/gvc will also run git commands?
  • git config --global alias.dvc '!dvc --git'
  • complete -F _dvc git-dvc

The idea is that e.g. dvc --git checkout <ID> or (imho better) git dvc checkout <ID> would do both checkouts.

[efiop]

Related #2363 #1551