[FEATURE REQUEST] Read checkout to be able to read data from staging area

[hhsecond]

Is your feature request related to a problem? Please describe.
Currently, read checkout won't be able to read data from the staging area. I was wondering what would be the technical difficulties for reading data from staging area

Describe the solution you'd like
repo.checkout(stage=True) or something similar could give access to the staging area. I think the major bottleneck from implementing this is the fact that the staging area could change and might even make the data unavailable. Maybe we could have a flag changes when the data changes and on read from a stage checkout, it could let the reading process know that the data changed (not the specific information but just that the data changed) and it can invalidate the checkout?

[rlizzo]

This isn't the craziest thing to do from a technical standpoint, but I'm wondering what the motivation for allowing this is?