Problem: Tracking parser revision in lockfile and allowing override
through the parsers module complicates the code. In addition, only
revision changes are handled robustly, not changes to other installation
info.
Solution: Track parser revision in the parsers module directly. Reload
parser table on every install or update call. Support modifying parser
table in a `User TSUpdate` autocommand.
Problem: Many parsers require node/npm to evaluate the `grammar.js`
before being able to generate a parser from it.
Solution: Generate from `grammar.json` instead, which is fully resolved.
Drops `node` and `npm` as (optional) requirements for nvim-treesitter.
Note that this requires parsers to commit the generated json iff the
grammar requires evaluation (which is currently the case for all tracked
languages).
If the plugin is loaded after a colorscheme is set that defines any of
these highlight groups, the default won't be applied. Subsequent
"highlight clear" commands (common when switching colorschemes) will
then clear any of those highlights, but these defaults never have
another opportunity to be initialized.
Effectively, if you load neovim with a colorscheme that has definitions
for some of these highlight groups, then load treesitter, then switch
colorschemes, many of these default links will be absent resulting in
colors that do not appear the same as if that colorscheme had been
used at startup.
Hooking the ColorScheme event with an autocmd that just reapplies these
defaults gives every colorscheme switch the opportunity to get the
defaults for non-explicitly-defined groups.
* set highlight groups via nvim_set_hl
* define autocommands via nvim_create_autocmd
* port plugin/nvim-treesitter.vim to Lua
* port healthcheck to Lua
