Allow interval per source to be overwritten to 0 to skip the source in this interval.

This change allows to overwrite an interval to 0 for a specific source in order to skip it for this interval.
This is useful if you have default intervals configured and you would like to skip certain sources for specific intervals.

ccollect

@@ -765,7 +765,7 @@ while [ "${source_no}" -lt "${no_sources}" ]; do
         oldest_bak=$(ls -${TSORT}1r | grep "^${INTERVAL}\\." | head -n 1 || \
             _exit_err "Listing oldest backup failed")
         _techo "Using ${oldest_bak} for destination dir ${destination_dir}"
-        if mv "${oldest_bak}" "${destination_dir}"; then
+        if mv "${oldest_bak}" "${destination_dir}" 2>/dev/null; then
             # Touch dest dir so it is not sorted wrong in listings below.
             ls_rm_exclude=$(basename "${destination_dir}")
 
@@ -779,7 +779,7 @@ while [ "${source_no}" -lt "${no_sources}" ]; do
         if [ "${remove}" -gt 0 ]; then
             _techo "Removing ${remove} backup(s)..."
 
-            if [ -z "${ls_rm_exclude}" ]; then
+            if [ -z "${ls_rm_exclude}" -o ${c_interval} -le 0 ]; then
                 # shellcheck disable=SC2010
                 ls -${TSORT}1r | grep "^${INTERVAL}\\." | head -n "${remove}" > "${TMP}" || \
                         _exit_err "Listing old backups failed"
@@ -793,6 +793,14 @@ while [ "${source_no}" -lt "${no_sources}" ]; do
         fi
     fi
 
+    #
+    # Skip backup of this source if interval is zero.
+    #
+    if [ ${c_interval} -le 0 ]; then
+        _techo "Skipping backup for this interval."
+        exit 0
+    fi
+
     #
     # Check for backup directory to clone from: Always clone from the latest one!
     # Exclude destination_dir from listing, it can be touched reused and renamed