Fix register corruption in CopyFile_EnsureDestFileWriteable

FileSwitch 2.90 introduced a register corruption bug in *Copy which
would (typically) result in an abort if the copy isn't going ahead
because the destination exists. This was down to the (undocumented)
input of R7 being corrupted by the call to EnsureCanonicalObject, and
not being restored before it gets used later on by the call to
Util_PrintName.

Fix the code to restore R7 before calling Util_PrintName, and update the
comments surrounding a couple of functions to make sure at least some of
the undocumented inputs are documented.

Fixes issue reported on forums:
https://www.riscosopen.org/forum/forums/4/topics/17802

Version 2.92. Tagged as 'FileSwitch-2_92'

VersionASM

@@ -9,12 +9,12 @@
                         GBLS    Module_ApplicationDate
                         GBLS    Module_HelpVersion
                         GBLS    Module_ComponentName
-Module_MajorVersion     SETS    "2.91"
-Module_Version          SETA    291
+Module_MajorVersion     SETS    "2.92"
+Module_Version          SETA    292
 Module_MinorVersion     SETS    ""
-Module_Date             SETS    "13 Mar 2023"
-Module_ApplicationDate  SETS    "13-Mar-23"
+Module_Date             SETS    "25 Mar 2023"
+Module_ApplicationDate  SETS    "25-Mar-23"
 Module_ComponentName    SETS    "FileSwitch"
-Module_FullVersion      SETS    "2.91"
-Module_HelpVersion      SETS    "2.91 (13 Mar 2023)"
+Module_FullVersion      SETS    "2.92"
+Module_HelpVersion      SETS    "2.92 (25 Mar 2023)"
                         END

VersionNum

-/* (2.91)
+/* (2.92)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  *
  */
-#define Module_MajorVersion_CMHG        2.91
+#define Module_MajorVersion_CMHG        2.92
 #define Module_MinorVersion_CMHG
-#define Module_Date_CMHG                13 Mar 2023
+#define Module_Date_CMHG                25 Mar 2023
 
-#define Module_MajorVersion             "2.91"
-#define Module_Version                  291
+#define Module_MajorVersion             "2.92"
+#define Module_Version                  292
 #define Module_MinorVersion             ""
-#define Module_Date                     "13 Mar 2023"
+#define Module_Date                     "25 Mar 2023"
 
-#define Module_ApplicationDate          "13-Mar-23"
+#define Module_ApplicationDate          "25-Mar-23"
 
 #define Module_ComponentName            "FileSwitch"
 
-#define Module_FullVersion              "2.91"
-#define Module_HelpVersion              "2.91 (13 Mar 2023)"
-#define Module_LibraryVersionInfo       "2:91"
+#define Module_FullVersion              "2.92"
+#define Module_HelpVersion              "2.92 (25 Mar 2023)"
+#define Module_LibraryVersionInfo       "2:92"

s/FSUtils

@@ -1455,6 +1455,9 @@ CopyDirectory Entry
 ; +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 ; See if the destination file already exists or is a dir
 
+; In    r7 = source file desc^, source exists !
+;       r8 = dest file desc^
+
 ; Out   Much corruption
 ;       r1, r6, fscb set up for dest
 
@@ -1521,6 +1524,7 @@ CopyFile_EnsureDestFileWriteable Entry "r7"
 
 
 20 ; Destination is a file or
+        FRAMLDR r7
 
         LDR     r14, util_bitset        ; Is source newer than dest ?
         TST     r14, #util_newer
@@ -1707,6 +1711,7 @@ fsw_already_exists_and_is_locked_confirm        DCB "CC10", 0
 
 ; +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 ; In    r5 = source object attributes
+;       r7 = source file desc^
 
 Copy_DeleteSourceAfterCopy Entry "r1"