Add HIDE / UNHIDE commands, to toggle the access "invisible" bit

This is used by the GS/OS Finder to conceal FINDER.DATA files.
Documented in "Exploring GS/OS and ProDOS 8" by Gary B. Little.
BASIC.SYSTEM's CAT/CATALOG are unaware of this, so the files are still
listed.

Note that the command is named "UNHIDE" rather than "SHOW" as that
sounds like a command to display file contents or something.

COMMANDS

@@ -11,3 +11,5 @@ mem
 online
 type
 touch
+hide
+unhide

README.md

@@ -55,6 +55,7 @@ Sample commands included:
     * `S` and `D` arguments can be used to specify slot and drive.
 * `BELL` - emits the standard Apple II beep
 * `BUZZ` - emits the ProDOS "nice little tone"
+* `HIDE` / `UNHIDE` - sets / clears the "invisible" bit on a file, used in GS/OS Finder
 
 
 ## Instructions For Developers

hide.cmd.s

@@ -0,0 +1,68 @@
+;;; ============================================================
+;;;
+;;; HIDE - Mark a file as invisible
+;;;
+;;; Usage: HIDE filename[,S#][,D#]
+;;;
+;;;  * filename can be relative or absolute path
+;;;
+;;; ============================================================
+
+        .include "apple2.inc"
+        .include "more_apple2.inc"
+        .include "prodos.inc"
+
+;;; ============================================================
+
+        .org $4000
+
+        ;; NOTE: Assumes XLEN is set by PATH
+
+        ;; Point BI's parser at the command execution routine.
+        lda     #<execute
+        sta     XTRNADDR
+        lda     #>execute
+        sta     XTRNADDR+1
+
+        ;; Mark command as external (zero).
+        lda     #0
+        sta     XCNUM
+
+        ;; Set accepted parameter flags
+
+        ;; Filename
+        lda     #PBitsFlags::FN1
+        sta     PBITS
+
+        ;; Slot & Drive handling
+        lda     #PBitsFlags::SD
+        sta     PBITS+1
+
+        clc                     ; Success (so far)
+rts1:   rts                     ; Return to BASIC.SYSTEM
+
+;;; ============================================================
+
+execute:
+        ;; Get the existing file info
+        lda     #$A
+        sta     SSGINFO
+        lda     #GET_FILE_INFO
+        jsr     GOSYSTEM
+        bcs     rts1
+
+;;; --------------------------------------------------
+
+        ;; Clear invisible bit
+        lda     FIACESS
+        ora     #ACCESS_I
+        sta     FIACESS
+
+        ;; Set new file info
+        lda     #$7
+        sta     SSGINFO
+
+        lda     #SET_FILE_INFO
+        jmp     GOSYSTEM
+
+;;; --------------------------------------------------

prodos.inc

@@ -33,6 +33,13 @@ FT_DIR  = $0F
 FT_CMD  = $F0
 FT_BAS  = $FC
 
+ACCESS_D  = %10000000           ; Access: Destroy-Enable
+ACCESS_RN = %01000000           ; Access: Rename-Enable
+ACCESS_B  = %00100000           ; Access: Backup
+ACCESS_I  = %00000100           ; Access: Invisible
+ACCESS_W  = %00000010           ; Access: Write-Enable
+ACCESS_R  = %00000001           ; Access: Read-Enable
+
 ;;; ============================================================
 ;;; BASIC.SYSTEM Global Page
 

unhide.cmd.s

@@ -0,0 +1,68 @@
+;;; ============================================================
+;;;
+;;; UNHIDE - Mark a file as not invisible
+;;;
+;;; Usage: UNHIDE filename[,S#][,D#]
+;;;
+;;;  * filename can be relative or absolute path
+;;;
+;;; ============================================================
+
+        .include "apple2.inc"
+        .include "more_apple2.inc"
+        .include "prodos.inc"
+
+;;; ============================================================
+
+        .org $4000
+
+        ;; NOTE: Assumes XLEN is set by PATH
+
+        ;; Point BI's parser at the command execution routine.
+        lda     #<execute
+        sta     XTRNADDR
+        lda     #>execute
+        sta     XTRNADDR+1
+
+        ;; Mark command as external (zero).
+        lda     #0
+        sta     XCNUM
+
+        ;; Set accepted parameter flags
+
+        ;; Filename
+        lda     #PBitsFlags::FN1
+        sta     PBITS
+
+        ;; Slot & Drive handling
+        lda     #PBitsFlags::SD
+        sta     PBITS+1
+
+        clc                     ; Success (so far)
+rts1:   rts                     ; Return to BASIC.SYSTEM
+
+;;; ============================================================
+
+execute:
+        ;; Get the existing file info
+        lda     #$A
+        sta     SSGINFO
+        lda     #GET_FILE_INFO
+        jsr     GOSYSTEM
+        bcs     rts1
+
+;;; --------------------------------------------------
+
+        ;; Set invisible bit
+        lda     FIACESS
+        and     #<(~ACCESS_I)
+        sta     FIACESS
+
+        ;; Set new file info
+        lda     #$7
+        sta     SSGINFO
+
+        lda     #SET_FILE_INFO
+        jmp     GOSYSTEM
+
+;;; --------------------------------------------------