When the caller needs a formatter, it's because they're doing
something non-trivial. When the user passed `--quiet` (see upcoming
patch), we should ideally skip doing related work for print the
formatting output. It helps if the `Ui` object doesn't even return a
`Formatter` then, so the caller is forced to handle the quiet case
differently.
Thanks to Yuya for the suggestion.
I'm going to reorganize CommandError as (kind, err, hints) tuple so that we
can add_hint() to the constructed error object.
Some config error messages are slightly adjusted because the inner error is
now printed in separate line.
This moves the config loading closer to CLI args where --tool=<name> option
will be processed. The factory function are proxied through the command helper
so that the base_ignores can be attached there later.
I'm going to add a prefix resolution method to OpStore, but OpStore is
unrelated to the index. I think ObjectId, HexPrefix, and PrefixResolution can
be extracted to this module.
It seems better to have the caller pass the transaction description
when we finish the transaction than when we start it. That way we have
all the information we want to include more readily available.
