feat: add command :SosBufToggle to toggle buffers

This command allows for ignoring individual buffers so that they do not
get autosaved. It accepts an optional `[bufname]` argument to specify a
buffer other than the current one. Deleting a buffer (e.g. `:bdelete`)
resets its ignored status. Ignore status is stored in the buffer
variable `b:sos_ignore`.

Also add dedicated API functions for this, as well as functions to
enable or disable the entire plugin. These can all be found in the
`require('sos')` module table.

Also do some refactoring/cleanup:

- Rename `lua/bufevents.lua` -> `lua/observer.lua`
- Remove `lua/plugin.lua` (require main module instead)
- Main module `require('sos')` is now the entry point (incl. when the
  plugin is sourced by nvim at startup) and also holds most of the
  plugin's state
- Make all config fields optional (in the class/type)
- Update `init.lua` to handle module reloading (UNFINISHED)
- Update `util.lua` with new utility functions and error handling
- Improve benchmark interface

lua/sos/_test/action.lua

@@ -0,0 +1,36 @@
+local util = require 'sos._test.util'
+local api = vim.api
+local M = { buf = {} }
+
+function M.input(keys)
+  api.nvim_feedkeys(
+    api.nvim_replace_termcodes(keys, true, true, true),
+    'L',
+    -- 'mtx',
+    false
+  )
+
+  util.await_schedule()
+end
+
+---NOTE: May change the current buffer!
+function M.trigger_save(buf)
+  if buf and buf ~= 0 and buf ~= api.nvim_get_current_buf() then
+    assert(api.nvim_buf_is_valid(buf), 'invalid buffer number: ' .. buf)
+    local ei = vim.o.ei
+    vim.o.ei = 'all'
+    api.nvim_set_current_buf(buf)
+    vim.o.ei = ei
+  end
+
+  M.input ':new<CR>'
+  vim.defer_fn(util.coroutine_resumer(false), 100)
+end
+
+function M.buf.modify()
+  assert.is_false(vim.bo.mod, 'buffer is modified prior to modification')
+  M.input 'ochanges<Esc>'
+  assert.is_true(vim.bo.mod, 'unable to modify buffer')
+end
+
+return M

lua/sos/_test/assert.lua

@@ -0,0 +1,38 @@
+local api = vim.api
+local M = {}
+
+function M.all_bufs_saved()
+  assert.same(
+    {},
+    vim.fn.getbufinfo { bufmodified = 1 },
+    'all buffers should be saved, and none modified'
+  )
+end
+
+---@param buf number
+function M.saved(buf)
+  vim.validate { buf = { buf, { 'number' }, false } }
+  local file = api.nvim_buf_get_name(buf)
+  assert.is_false(vim.bo[buf].mod, 'buffer is still modified')
+  assert.same(
+    api.nvim_buf_get_lines(file, 0, -1, true),
+    vim.fn.readfile(file),
+    "buffer wasn't saved"
+  )
+end
+
+---@param buf number
+function M.unsaved(buf)
+  vim.validate { buf = { buf, { 'number' }, false } }
+  local file = api.nvim_buf_get_name(buf)
+  assert.is_true(vim.bo[buf].mod, "buffer shouldn't have been saved")
+  local ok, content = pcall(vim.fn.readfile, file)
+  if not ok then return end
+  assert.not_same(
+    api.nvim_buf_get_lines(file, 0, -1, true),
+    content,
+    "buffer shouldn't have been saved"
+  )
+end
+
+return M

lua/sos/_test/util.lua

@@ -4,7 +4,7 @@
 
 local M = {}
 local api = vim.api
-local uv = vim.loop
+local uv = vim.uv or vim.loop
 local sleep = uv.sleep
 local co = coroutine
 local tmpfiles
@@ -74,18 +74,20 @@ function M.bufwritemock(onwrite)
   })
 end
 
+---@return integer bufnr
 ---@return string output
----@overload fun(nvim: table, file?: string): string
----@overload fun(file?: string): string
+---@overload fun(nvim: table, file?: string)
+---@overload fun(file?: string)
 function M.silent_edit(...)
   local external_nvim_or_api, file = M.nvim_recv_or_api(...)
-
-  return external_nvim_or_api.nvim_cmd({
+  local out = external_nvim_or_api.nvim_cmd({
     cmd = 'edit',
     args = { file },
     magic = { file = false, bar = false },
     mods = { silent = true },
   }, { output = true })
+
+  return api.nvim_get_current_buf(), out
 end
 
 ---@param keys string
@@ -386,7 +388,7 @@ end
 ---@param fn function
 ---@return number ns
 function M.time_it_once(fn)
-  local hrtime = vim.loop.hrtime
+  local hrtime = uv.hrtime
   local start = hrtime()
   fn()
   return hrtime() - start
@@ -427,7 +429,7 @@ end
 ---@param cb function
 ---@return unknown
 function M.set_timeout(ms, cb)
-  local timer = vim.loop.new_timer()
+  local timer = uv.new_timer()
 
   timer:start(ms, 0, function()
     timer:stop()

lua/sos/autocmds.lua

@@ -1,5 +1,4 @@
 local M = {}
-local commands = require 'sos.commands'
 local impl = require 'sos.impl'
 local api = vim.api
 local augroup = 'sos-autosaver'