* Mitigate history file bug in Rustyline
Rustyline's duplicate ignoring code has a bug that can cause data loss and
history file corruption. Testing seems to indicate that disabling this behavior
and allowing duplicates will prevent the bug from showing up. Many people have
complained about this issue, I think it is worthwhile to fix the bug at the cost
of permitting duplicate history entries.
Upstream bug: https://github.com/kkawakam/rustyline/issues/559
* Increase Rustyline historyfile limit
Rustyline will only store 100 history items by default. This is quite a small
limit for a shell that people use as a daily driver. Especially when the
deduplication code is removed, we will hit that limit quickly and start to lose
history. This commit bumps the limit up to 10k. We can discuss if this is an
inappropriate limit or if we should allow users to specify this setting in their
nushell config file instead.
Seems we do `ctrl` feature checks in `nu-cli` and `nu-command`. We should find a better way to report the enabled features un the `version` command without using the conditionals (or somewhere else)
In Nu we have variables (E.g. $var-name) and these contain `Value` types.
This means we can bind to variables any structured data and column path syntax
(E.g. `$variable.path.to`) allows flexibility for "querying" said structures.
Here we offer completions for these. For example, in a Nushell session the
variable `$nu` contains environment values among other things. If we wanted to
see in the screen some environment variable (say the var `SHELL`) we do:
```
> echo $nu.env.SHELL
```
with completions we can now do: `echo $nu.env.S[\TAB]` and we get suggestions
that start at the column path `$nu.env` with vars starting with the letter `S`
in this case `SHELL` appears in the suggestions.
We've relied on `clap` for building our cli app bootstrapping that figures out the positionals, flags, and other convenient facilities. Nu has been capable of solving this problem for quite some time. Given this and much more reasons (including the build time caused by `clap`) we start here working with our own.
* enable theming of the command line syntax
* added missing flatshape, sorted flatshapes for easier reading.
* sorted flat shapes again and saved it this time
* added sample rwb.json syntax them file to docs
