Made -compare and -update work with recorded MD5 sums

xorriso/xorriso.1

@@ -2,7 +2,7 @@
 .\" First parameter, NAME, should be all caps
 .\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
 .\" other parameters are allowed: see man(7), man(1)
-.TH XORRISO 1 "Aug 19, 2009"
+.TH XORRISO 1 "Aug 20, 2009"
 .\" Please adjust this date whenever revising the manpage.
 .\"
 .\" Some roff macros, for reference:
@@ -697,6 +697,7 @@ automatic last minute changes before the session gets written. Command
 e.g. if you need to apply filters to all updated files.
 .br
 Mode "without_update" avoids hardlink processing during update commands.
+Use this if your filesystem situation does not allow -disk_dev_ino "on".
 .br
 xorriso commands which extract files from an ISO image try to hardlink files
 with identical inode number. The normal scope of this operation is from
@@ -734,6 +735,11 @@ checksums tags of superblock and directory tree match properly. The MD5
 checksums of data files and whole session get loaded from the image if there
 are any.
 .br
+With options -compare and -update the eventually recorded MD5 of a file
+will be used to avoid content reading from the image. Only the disk file
+content will be read and compared with that MD5. This can save much time
+if -disk_dev_ino "on" is not suitable.
+.br
 At image generation time they are computed for each file which gets its data
 written into the new session. The checksums of files which have their data
 in older sessions get copied into the new session. Superblock, tree and whole
@@ -770,6 +776,9 @@ same filesystems. Use this if mode "on" always sees all files changed.
 .br
 The speed advantage appears only if the loaded session was produced with
 -disk_dev_ino "on" too.
+.br
+Note that -disk_dev_ino "off" is totally in effect only if -hardlinks is "off",
+too.
 .TP
 \fB\-rom_toc_scan\fR "on"|"off"[:"emul_on"|"emul_off"]
 Read-only drives do not tell the actual media type but show any media as