Mac: Ensure that the kext blocks file I\O that that is not allowed when VFSForGit is unmounted

We used to have this on Mac, but it had to be removed in #191 as it was preventing:

• VFS4G from modifying the .git/hooks a as part of mounting
• gvfs repair from being able to fix up files in the .git folder

As the feature is re-enabled we’ll need to consider how we can still support the scenarios above. Perhaps we can support a new xattr that VFS4G sets on folders letting the kext know that offline modifications are allowed? Or maybe there is some way that we can ACL/mark the VFS4G processes so that the kext knows that they should be allowed to make offline modifications?

[wilbaker]

@pmj thanks!

I think we can close this out.

Regarding this item:

Delete operations that are for renames (i.e. moving a file out of the offline repo)

I think we can stick with the current behavior and adjust it later if we get feedback that the current behavior is undesirable.

I’d agree, let’s cover that as part of #457.

I’ve updated the description of #457 to include this work.

[pmj]

With #1429 done, there’s now not much left to do here. A few loose ends:

[@wilbaker] Ideally we’d block these as well:

• Delete operations that are for renames (i.e. moving a file out of the offline repo)

This is now implemented for empty files. I think that’s what we want: we already allow deleting files for other reasons than renaming, and I think it’s reasonable to allow a user to move hydrated or full files out of the repo, possibly in order to back up some work they did before deleting the repo entirely.

• Moving files into the offline repo (not sure if we’d get a KAUTH_VNODE_ADD_FILE for this)

We do indeed get a callback with that action, or KAUTH_VNODE_ADD_SUBDIRECTORY if the thing being moved is a directory, and both are now blocked on offline roots as of #1429.

• Mode changes to placeholders (both empty and hydrated) in the offline root. Note that we still have #457 to detect mode changes in the first place, and so we might not be able to add that check now.

I think this will be a case of blocking KAUTH_VNODE_WRITE_SECURITY when offline, but I’d have to check - and yes, I’d agree, let’s cover that as part of #457.