Allow session management to have a delayed start.

[mahlonsmith]

I'm really enjoying the simplicity of persistence, but coming from Obsession, there's a few things I was wanting, and I think this patch addresses them all.

• I use nvim for all sorts of sysadmin stuff, I don't need session files getting littered around unless I'm actually in a project that warrants it -- I want control over when to start and stop the management
• I'd like to have a way to ask the plugin if it's currently active or not (a cleaner way might be to just check for the existence of the 'persistence' augroup, but I didn't find any methods to do that.)
• Similarly, I'd like to ask the plugin if a session file is present for some basic boolean stuff.

With this patch, I can integrate things with lualine,

local function sessionRunning()
    if require( 'persistence' ).running then
        return ''
    else
        return ''
    end
end

... dashboard,

shortcut = {
    {
        desc = '↪️ Restore Session ',
        action = function()
            persistence = require( 'persistence' )
            if persistence.has_session() then
                persistence.load()
            else
                print "No session for this directory."
            end
        end,
        key = 's',
    },

and have a global "on/off" switch for only starting up a session when I want:

require( 'persistence' ).setup({
    auto_start = false
})

-- Toggle session tracking for current directory.
--
vim.keymap.set( '', '<F8>', function()
    local persistence = require( 'persistence' )
    if persistence.running then
        persistence.stop()
        print "Disabled session tracking."
    else
        persistence.start()
        print "Enabled session tracking."
    end
end, { desc = "Toggle session tracking" })

This also indirectly fixes stuff like #14 as a possible alternative option.

Default behavior is exactly as-is, this shouldn't change anything for existing installations.

[github-actions[bot]]

This PR is stale because it has been open 60 days with no activity.

[folke]

require("persistence").active()