doc: fixes for spawn.with_line_callback

lib/awful/spawn.lua

@@ -129,20 +129,22 @@ function spawn.with_shell(cmd)
     end
 end
 
---- Spawn a program and asynchronously and capture its output line by line.
+--- Spawn a program and asynchronously capture its output line by line.
 -- @tparam string|table cmd The command.
--- @tab callbacks Table containing callbacks that should be
+-- @tab callbacks Table containing callbacks that should be invoked on
---   invoked on various conditions.
+--   various conditions.
--- @tparam[opt] function callbacks.stdout Function that is called with each line of
+-- @tparam[opt] function callbacks.stdout Function that is called with each
---   output on stdout, e.g. `stdout(line)`.
+--   line of output on stdout, e.g. `stdout(line)`.
--- @tparam[opt] function callbacks.stderr Function that is called with each line of
+-- @tparam[opt] function callbacks.stderr Function that is called with each
---   output on stderr, e.g. `stderr(line)`.
+--   line of output on stderr, e.g. `stderr(line)`.
--- @tparam[opt] function callbacks.output_done Function to call when no more output
+-- @tparam[opt] function callbacks.output_done Function to call when no more
---   is produced.
+--   output is produced.
--- @tparam[opt] function callbacks.exit Function to call when the spawned process
+-- @tparam[opt] function callbacks.exit Function to call when the spawned
--- exits. This function gets the exit reason and code as its argument. The
+--   process exits. This function gets the exit reason and code as its
--- reason can be "exit" or "signal". For "exit", the second argument is the exit
+--   arguments.
--- code. For "signal", the second argument is the signal causing process
+--   The reason can be "exit" or "signal".
+--   For "exit", the second argument is the exit code.
+--   For "signal", the second argument is the signal causing process
 --   termination.
 -- @treturn[1] Integer the PID of the forked process.
 -- @treturn[2] string Error message.