Update default.conf

More explanatory comment in default.conf
how COPY_AS_IS versus LIBS, PROGS,
and REQUIRED_PROGS are meant to be used, cf.
#2278 (comment)

usr/share/rear/conf/default.conf

@@ -1230,6 +1230,21 @@ FIRMWARE_FILES=()
 UDEV_NET_MAC_RULE_FILES=( /etc/udev/rules.d/*persistent*{names,net,cd}.rules /etc/udev/rules.d/*eno-fix.rules )
 
 # Files and directories to copy as-is (with tar) into the ReaR recovery system.
+# As its name tells COPY_AS_IS is primarily meant to "only copy as is".
+# To get libraries into the recovery system, use the LIBS array.
+# To get non-mandatory programs into the recovery system, use the PROGS array.
+# To get mandatory programs into the recovery system, use the REQUIRED_PROGS array.
+# For elements in the LIBS, PROGS, and REQUIRED_PROGS arrays
+# the RequiredSharedObjects function is called to determine required
+# shared objects (libraries) that get also copied into the recovery system.
+# For elements in the COPY_AS_IS array there is an exception to the
+# above "only copy as is" rule that for files in the COPY_AS_IS array
+# that have the executable permission bit set RequiredSharedObjects is called
+# to also get their needed libraries copied into the recovery system.
+# But for libraries in the COPY_AS_IS array that do not have the executable
+# permission bit set no dependant other libraries get copied.
+# The reasoning behind is that programs in the COPY_AS_IS array
+# are handled gracefully but COPY_AS_IS is not meant for libraries.
 # Usually globbing patterns in COPY_AS_IS are specified without quoting
 # like COPY_AS_IS+=( /my/directory/* /path/to/my/files* )
 # so that the bash pathname expansion works as usually intended