Previously, a depth:0 query produced an empty report (since there are no
level zero accounts). Now, it aggregates all data into one summary item
with account name "...".
This makes it easier to see the kind of data Gwern was looking for from
register-csv (net worth over time). Eg this shows one line per month
summarising the total of assets and liabilities:
hledger register-csv -- -MHE ^assets ^liabilities depth:0
Single and multi-column balance reports behave similarly.
Changes include:
- flat mode now shows exclusive (subaccount-excluding) balances.
This is a deviation from ledger, but seems simpler and clearer
for users and implementors across the various modes.
- in flat mode, --depth now aggregates deeper accounts at the
depth limit, rather than just excluding them from the report.
This is more useful.
- in flat mode, --empty no longer shows parent accounts with
no postings.
- more tests, more debug output, clearer code
