diff fails on empty repository

[marstr]

System Information

Version:  v0.2.0-alpha-modified
System: linux/amd64
Go:  go1.14.2
Source Revision:  16abc7be5a5ad17a0aeb0f1a7815f5e13a67bd1b

What did you do?

baronial init
mkdir accounts/checking
mkdir -p budget/food/grocery
baronial credit 10.89 ./accounts/checking/ ./budget/food/grocery/
baronial diff

What did you expect to happen?

A summary of the 10.89 being added to the checking account and grocery budget should have been printed.

What actually happened?

An error message was spat out, complaining that 0000000000000000000000000000000000000000.json doesn't exist.

Stack Trace

ERRO[0000] open /home/marstr/.tmp/tmp.7w3FkcD1mq/.baronial/objects/0000000000000000000000000000000000000000.json: no such file or directory 
Error: exec: not started
Usage:
  baronial diff [refspec] [refspec] [flags]
Flags:

-h, --help   help for diff
exec: not started