when calling rev-list, HEAD was passed as a default argument: git rev-list HEAD --count but HEAD is only populated when we perform git.Open; it is zeroed out when we perform git.PlainOpen: git rev-list 00000... --count this causes rev-list to exit with an error, when used in repos that are git.PlainOpen'd. Signed-off-by: oppiliappan <me@oppi.li>