sh: Add shutdown command

applications/sh/commands/commands.asm

@@ -33,6 +33,11 @@ shell_parse_command:
     call compare_string
     ifz jmp shell_help_command
 
+    ; shutdown
+    mov r1, shell_shutdown_command_string
+    call compare_string
+    ifz jmp shell_shutdown_command
+
     ; type
     mov r1, shell_type_command_string
     call compare_string
@@ -57,3 +62,4 @@ shell_invalid_command_string: data.str "invalid command or FXF binary" data.8 10
     #include "commands/exit.asm"
     #include "commands/help.asm"
     #include "commands/type.asm"
+    #include "commands/shutdown.asm"

applications/sh/commands/help.asm

@@ -21,6 +21,7 @@ shell_help_text:
     data.str "exit    | exit the shell" data.8 10
     data.str "help    | show this help text" data.8 10
     data.str "type    | print file $0 of type $1" data.8 10
+    data.str "shutdown| turn the computer off" data.8 10
     data.8 10
     data.str "type the name of an FXF binary to launch" data.8 10
     data.str "it as a new task; the shell will suspend" data.8 10

applications/sh/commands/shutdown.asm

@@ -0,0 +1,7 @@
+; shutdown command
+
+shell_shutdown_command_string: data.str "shutdown" data.8 0
+
+shell_shutdown_command:
+    call poweroff
+    ret