Reorganize internal functions

src/lib/internals/locate-target.sh

@@ -0,0 +1,15 @@
+locate-target() {
+  if [ -n "$TARGET" ]; then
+    if [ ! -d "$TARGET" ]; then
+      echo "ERROR: Target \"$TARGET\" is not a directory." >&2
+      return 1
+    fi
+  elif [ -n "$HOME" ] && [ -d "$HOME" ]; then
+    TARGET="$HOME"
+  elif [ -d ~ ]; then
+    TARGET=~
+  else
+    echo "ERROR: Your \$HOME folder could not be found." >&2
+    return 1
+  fi
+}