Finished Fish Completer

[jdugan6240]

The following is a finished, working completer using the fish shell to generate completions (thanks @TorchedSammy for the help!):

-- Utility for using fish completions in Hilbish.
fish_completer = function(query, ctx, fields)
    -- Ensure any quotes in input are properly escaped
    ctx = ctx:gsub('"', '\\"')
    ctx = ctx:gsub("'", "\\'")

    -- Run fish
    local cmd = "fish --command 'complete \"--do-complete=" .. ctx .. "\"'"
    local res = io.popen(cmd)
    local raw_str = res:read('*all')

    -- Extract completion items
    local values = table.map(string.split(raw_str, "\n"), function(v)
        return string.split(v, "\t")[1]
    end)

    -- Only extract completions that start with given prefix
    -- (fish doesn't consistently do this it seems)
    if query ~= "" then
        for i = #values,1,-1 do
            if values[i]:find(query, 1, True) ~= 1 then
                table.remove(values, i)
            end
        end
    end

    -- Construct completion items table
    local comp = {
        {
            items = values,
            type = 'grid'
        }
    }

    return comp, query
end

This completer would be used as follows:
hilbish.complete('command.git', fish_completer)