backup-tar: Make standalone config file possible

backup-tar/backup.sh

@@ -13,11 +13,16 @@ fail() {
     exit 1
 }
 
-SHORT_HOST=$(hostname -s)
-TARGET=backup-$SHORT_HOST@antea
-SOURCES_FILE=$SCRIPT_DIR/sources_$SHORT_HOST
-. $SOURCES_FILE
-[[ $SOURCES ]] || fail "SOURCES expected to be set in $SOURCES_FILE"
+if [[ $1 ]]; then
+    . $1
+else
+    SHORT_HOST=$(hostname -s)
+    TARGET=backup-$SHORT_HOST@antea
+    SOURCES_FILE=$SCRIPT_DIR/sources_$SHORT_HOST
+    . $SOURCES_FILE
+fi
+[[ $TARGET ]] || fail "TARGET expected to be set in config"
+[[ $SOURCES ]] || fail "SOURCES expected to be set in $SOURCES_FILE or config"
 TIMESTAMP=$(date +"%Y-%m-%d")
 
 mkdir lock || fail "ERROR: backup already in progress (lock dir exists)"