repo.index create new index on ever reference - surprising

[barry-scott]

was surprised to find that the index property of Repo created a new IndexFile object on each reference. This would have lead to code with terrible performance if I had not read the source and discovered this. At a minimum this needs a warning in docs.

I would suggest that you either make index stable until the user asked for it to be updated.
Or drop the property in favor of a function that returns a new IndexFile().

[barry-scott]

The same property does lots of work goes for untracked_files as well.

[Byron]

I agree, GitPython has some properties which can be costly, and the examples you provide are good ones indeed.
For now I think it's best to make this clear in the documentation.