This PR:
1. Adds basic support for `CustomValue` to `explore`. Previously `open
foo.db | explore` didn't really work, now we "materialize" the whole
database to a `Value` before loading it
2. Adopts `anyhow` for error handling in `explore`. Previously we were
kind of rolling our own version of `anyhow` by shoving all errors into a
`std::io::Error`; I think this is much nicer. This was necessary because
as part of 1), collecting input is now fallible...
3. Removes a lot of `explore`'s fancy command help system.
- Previously each command (`:help`, `:try`, etc.) had a sophisticated
help system with examples etc... but this was not very visible to users.
You had to know to run `:help :try` or view a list of commands with
`:help :`
- As discussed previously, we eventually want to move to a less modal
approach for `explore`, without the Vim-like commands. And so I don't
think it's worth keeping this command help system around (it's
intertwined with other stuff, and making these changes would have been
harder if keeping it).
4. Rename the `--reverse` flag to `--tail`. The flag scrolls to the end
of the data, which IMO is described better by "tail"
5. Does some renaming+commenting to clear up things I found difficult to
understand when navigating the `explore` code
I initially thought 1) would be just a few lines, and then this PR blew
up into much more extensive changes 😅
## Before
The whole database was being displayed as a single Nuon/JSON line 🤔
## After
The database gets displayed like a record
## Future work
It is sort of annoying that we have to load a whole SQLite database into
memory to make this work; it will be impractical for large databases.
I'd like to explore improvements to `CustomValue` that can make this
work more efficiently.
