Improve testability of the Real interpreter

[teggotic]

There is an issue in how we test actions. Fundamentally, we rely on the fact that the Real runner is generating git calls correctly. This could be neglected in theory, but there is another issue, which forces us to generate "textual" representation of what our command is doing, in multiple places, which leads to code repetition.
As a solution to this, I've created 1 data type for every type of the command we can execute, and implemeted the way to render it to the "textual" representation.
This could be used by Real runner directly, but this still suffers from a different issue. We give Real runner to much access, by adding MonadIO to the context.
There is a solution however. We can create a custom Monad which can provide all needed functions for Real to proceed. Going this way, we can hide how we "render" and "execute" git calls from the Real runner, which implies that it has no way to run arbitrary commands at all.

Values to git config should be quoted to work properly, otherwise they
(specifically aliases) would be set as multi-value configs.

However, if we just blindly change this to be quoted values, we would
split them into separate arguments for a proc, which would lead to the
same issue.
To improve this, we just need to use [] instead of Text for command
args.

Note: I've switched to "raw strings" ([s|quoted "string"|]) in
AcquireRepositorySpec.hs to remove escaping of double quotes.

#299

The contribution:

• updates all affected documentation
• provides commits messages which comply with the CONTRIBUTING.md > Committing the changes rules
• updates the completion scripts if requires
• complies with all requirements from README.md > Hands-on development notes

@bees-hive/elegant-git-maintainers, please review.

[extsoft]

@teggotic please resolve conflicts here

[teggotic]

@teggotic please resolve conflicts here

Sure, @extsoft please check