Rewrite the git help parser #50
Description
Currently this parser extracts options from git help pages lazily (only after the command is first referenced) which works decently well. This is then used for syntax highlighting and completions.
The problem is that this approach doesn't parse the SYNOPSIS and COMMANDS sections which would allow for richer completions.
It'd be great to rewrite the code to have an explicit parser class to be able to better parse these different sections. This could also facilitate more context based completions as well for things like git commits or branches.