Refine exit commands (#7)

* Change q[uit]! command's behavior

- `quit`, `q` - quit with confirmation
- `quit!`, `q!` - quit immediately

Author: st0012

README.md

@@ -321,10 +321,14 @@ The `<...>` notation means the argument.
   * Finish this frame. Resume the program until the current frame is finished.
 * `c[ontinue]`
   * Resume the program.
-* `q[uit]` or exit or `Ctrl-D`
+* `q[uit]` or `Ctrl-D`
   * Finish debugger (with the debuggee process on non-remote debugging).
-* `kill` or `q[uit]!`
-  * Stop the debuggee process.
+* `q[uit]!`
+  * Same as q[uit] but without the confirmation prompt.
+* `kill`
+  * Stop the debuggee process with `Kernal#exit!`.
+* `kill!`
+  * Same as kill but without the confirmation prompt.
 
 ### Breakpoint
 

lib/debug/session.rb

@@ -231,25 +231,36 @@ def wait_command
       when 'c', 'continue'
         @tc << :continue
 
-      # * `q[uit]` or exit or `Ctrl-D`
+      # * `q[uit]` or `Ctrl-D`
       #   * Finish debugger (with the debuggee process on non-remote debugging).
-      when 'q', 'quit', 'exit'
+      when 'q', 'quit'
         if ask 'Really quit?'
           @ui.quit arg.to_i
           @tc << :continue
         else
           return :retry
         end
 
-      # * `kill` or `q[uit]!`
-      #   * Stop the debuggee process.
-      when 'kill', 'quit!', 'q!'
+      # * `q[uit]!`
+      #   * Same as q[uit] but without the confirmation prompt.
+      when 'q!', 'quit!'
+        @ui.quit arg.to_i
+        @tc << :continue
+
+      # * `kill`
+      #   * Stop the debuggee process with `Kernal#exit!`.
+      when 'kill'
         if ask 'Really kill?'
           exit! (arg || 1).to_i
         else
           return :retry
         end
 
+      # * `kill!`
+      #   * Same as kill but without the confirmation prompt.
+      when 'kill!'
+        exit! (arg || 1).to_i
+
       ### Breakpoint
 
       # * `b[reak]`
@@ -417,7 +428,7 @@ def wait_command
       #   * Show the result of `<expr>` at every suspended timing.
       when 'display'
         if arg && !arg.empty?
-          @displays << arg 
+          @displays << arg
           @tc << [:eval, :try_display, @displays]
         else
           @tc << [:eval, :display, @displays]
@@ -808,7 +819,7 @@ def stop_all_threads
       end
     end
 
-    ## event 
+    ## event
 
     def on_load iseq, src
       @sr.add iseq, src