basic impl

try

@@ -72,6 +72,22 @@ try() {
     findmnt --real -r -o target -n >>"$DIRS_AND_MOUNTS"
     sort -u -o "$DIRS_AND_MOUNTS" "$DIRS_AND_MOUNTS"
 
+    # Setup excluded entries
+    excldir="$SANDBOX_DIR/excldir"
+    if [ -n "$EXCL_ENTS" ]
+    then
+        OLDIFS=$IFS
+        IFS=":"
+        mkdir "$excldir"
+        for exclent in $EXCL_ENTS
+        do
+            whiteout_file="$SANDBOX_DIR/excldir/$(realpath "$exclent")"
+            mkdir -p "$(dirname "$whiteout_file")"
+            mknod "$whiteout_file" c 0 0
+        done
+        IFS=$OLDIFS
+    fi
+
     # Calculate UPDATED_DIRS_AND_MOUNTS that contains the merge arguments in LOWER_DIRS
     UPDATED_DIRS_AND_MOUNTS="$(mktemp --suffix ".try-$EXECID")"
     export UPDATED_DIRS_AND_MOUNTS
@@ -81,6 +97,11 @@ try() {
         OLDIFS=$IFS
         IFS=":"
 
+        if [ -d "$excldir/$mountpoint" ]
+        then
+            new_mountpoint="$excldir/$mountpoint"
+        fi
+
         for lower_dir in $LOWER_DIRS
         do
             temp_mountpoint="$lower_dir/upperdir$mountpoint"
@@ -614,7 +635,7 @@ NO_COMMIT="interactive"
 # Includes all patterns given using the `-i` flag; will be used with `grep -f`
 IGNORE_FILE="$(mktemp --suffix ".try-$EXECID")"
 
-while getopts ":yvnhxi:D:U:L:" opt
+while getopts ":yvnhxi:D:U:L:E:" opt
 do
     case "$opt" in
         (y)   NO_COMMIT="commit";;
@@ -632,6 +653,12 @@ do
               fi
               LOWER_DIRS="$OPTARG"
               NO_COMMIT="quiet";;
+        (E)   if [ -n "$EXCL_ENTS" ]
+              then
+                  error "the -E option has been specified multiple times" 2
+              fi
+              EXCL_ENTS="$OPTARG"
+              NO_COMMIT="quiet";;
         (v)   echo "$TRY_COMMAND version $TRY_VERSION" >&2
               exit 0;;
         (U)   if ! [ -x "$OPTARG" ]