Partial Clone: Commands that could be problematic

We discussed partial clone today during the contributor's summit. There were some concerns about some commands that would cause over-hydration of blobs that need server requests to resolve.

GVFS blocks "fsck", "gc", "prune", "repack", "submodule", and "worktree" [1]. I promised I would include this list. There are a few limitations on the arguments of the other commands, as seen in that code. These commands that are blocked are already handled in partial clone with the "promisor" pattern. The "worktree" limitation is only due to the file-system virtualization layer of GVFS.

We discussed commands like "git grep" that sometimes look at the working directory and sometimes crawls trees. That is a command that should be considered for batching object downloads, limiting the command to "hydrated" blobs, or limiting to a sparse checkout.

Thanks,

-Stolee

[1] https://github.com/Microsoft/GVFS/blob/2db0c030eb257beebf8e17f1c2ce72ffb166f533/GVFS/GVFS.Hooks/Program.cs#L120-L137