feat: Add helper variable for optimization

src/lib/source.sh

@@ -37,7 +37,7 @@ validate_sources() {
 }
 
 validate_targets() {
-    # Check targets array and set __main_target variable.
+    # Check targets array and set __main_target and __main_target_path
     #
     # Usage: validate_targets ARRAY
 
@@ -71,9 +71,9 @@ validate_targets() {
         # Fail if __main_target's path is not a directory
         parse_uri "$__main_target"
         if [ -d "$path" ]; then
-            __main_target="$path"
+            __main_target_path="$path"
         else
-            echo "Error: Path $path in $__main_target" \
+            echo "Error: Path '$path' from URI '$__main_target'" \
                 "is not directory or does not exists" >&2
             exit 1
         fi
@@ -120,4 +120,5 @@ is_function_set() {
     # Usage: is_function_set FUNCTION
 
     declare -F -- "$1" > /dev/null
+    return "$?"
 }