File logging (#1053)

* add file logging infrastructure

* log git runner operations

* log configuration and mappings

* document file logging infrastructure

* style fixes

* stylua fixes

* document log file locations

lua/nvim-tree/log.lua

@@ -0,0 +1,40 @@
+local M = {
+  config = nil,
+  path = nil,
+}
+
+--- Write to log file
+--- @param typ as per log.types config
+--- @param fmt for string.format
+--- @param ... arguments for string.format
+function M.raw(typ, fmt, ...)
+  if not M.path or not M.config.types[typ] and not M.config.types.all then
+    return
+  end
+
+  local line = string.format(fmt, ...)
+  local file = io.open(M.path, "a")
+  io.output(file)
+  io.write(line)
+  io.close(file)
+end
+
+-- Write to log file
+-- time and typ are prefixed and a trailing newline is added
+function M.line(typ, fmt, ...)
+  if not M.path or not M.config.types[typ] and not M.config.types.all then
+    return
+  end
+
+  M.raw(typ, string.format("[%s] [%s] %s\n", os.date "%H:%M:%S", typ, fmt), ...)
+end
+
+function M.setup(opts)
+  M.config = opts.log
+  if M.config and M.config.enable and M.config.types then
+    M.path = string.format("%s/nvim-tree-%s-%s.log", vim.fn.stdpath "cache", os.date "%H:%M:%S", vim.env.USER)
+    print("nvim-tree.lua logging to " .. M.path)
+  end
+end
+
+return M