New command -iso_nowtime to set fixed timestamp for synthetic files

xorriso/xorriso.texi

@@ -50,7 +50,7 @@
 @c man .\" First parameter, NAME, should be all caps
 @c man .\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
 @c man .\" other parameters are allowed: see man(7), man(1)
-@c man .TH XORRISO 1 "Version 1.5.1, Feb 16, 2019"
+@c man .TH XORRISO 1 "Version 1.5.1, Apr 15, 2019"
 @c man .\" Please adjust this date whenever revising the manpage.
 @c man .\"
 @c man .\" Some roff macros, for reference:
@@ -1269,6 +1269,16 @@ lowercase letters. This is compatible to default GNU/Linux mount behavior.
 Mode "uppercase" is like "stripped" but maps lowercase letters to uppercase,
 if any occur despite the prescriptions of ECMA-119.
 @c man .TP
+@item -iso_nowtime "dynamic"|timestring
+@kindex -iso_nowtime    fixed "now" time for ISO 9660 objects
+@cindex libisofs, fixed "now" time
+Choose whether to use the current time ("dynamic") or a fixed time point
+for timestamps of ISO 9660 nodes without a disk source file and as default
+for superblock timestamps.
+@*
+If a timestring is given, then it is used for such timestamps. For the formats
+of time strings see command @strong{-alter_date}.
+@c man .TP
 @item -disk_dev_ino "on"|"ino_only"|"off"
 @kindex -disk_dev_ino   fast incremental backup
 @cindex Backup, enable fast incremental, -disk_dev_ino
@@ -7149,7 +7159,8 @@ It is supposed to be either undefined or to contain a decimal number
 which tells the seconds since january 1st 1970. If it contains a number,
 then it is used as time value to set the default of
 -volume date "uuid", sets -boot_image "any" "gpt_disk_guid=" to
-"volume_date_uuid", and -volume_date "all_file_dates" to "set_to_mtime",
+"volume_date_uuid", -volume_date "all_file_dates" to "set_to_mtime",
+and -iso_nowtime to "=$SOURCE_DATE_EPOCH".
 @*
 Startup files and program options can override the effect of SOURCE_DATE_EPOCH.
 @*