From elsewhere, an install is seeing fetches of observed repositories occasionally fail with an error like this:
Error updating working copy: Failed to fetch changes! COMMAND git fetch origin '+refs/*:refs/*' --prune STDOUT (empty) STDERR error: Could not read <... hash ...> fatal: pack has 1 unresolved delta fatal: index-pack failed
The only way to recover these working copies appears to be destroy and re-clone them.