ci-fairy: do not import git from the top
cc @tanty
This MR is identical to !61 (closed) but with the ci-fairy shas updated so we can merge this.
From the commit:
The GitPython module depends in the git command.
Installing git pulls quite some dependencies: eg. in a Debian Buster
system it increases the used space in ~100MB.
We may want to use some of the ci-fairy commands in systems with
constrained space. Since git is used only in some of the commands,
let's import only when it's really needed.
v2:
- Remove the get_git() helper and patch the git module at
sys.modules in the tests (Peter).
Closes !61 (closed)