fix: make sure that files with + in their name get escaped

otherwise if you have a command like g++, csv++ you will see the
following error:

 grep: repetition-operator operand invalid

MINOR: fixes a bug for keys with `+` characters

lib/utils.bash

@@ -367,7 +367,7 @@ get_preset_version_for() {
 
 get_asdf_config_value_from_file() {
   local config_path=$1
-  local key=$2
+  local key=$(escape_regexp $2)
 
   if [ ! -f "$config_path" ]; then
     return 1
@@ -628,6 +628,12 @@ is_executable() {
   return 1
 }
 
+escape_regexp() {
+  # if the plugin in question has special characters (+, ., * or ?) it will cause any grep or sed
+  # calls with that plugin name to fail
+  printf "%s" $1 | sed -e "s/\([.+*?]\)/\\\\\1/g"
+}
+
 plugin_shims() {
   local plugin_name=$1
   local full_version=$2

test/utils.bats

@@ -460,3 +460,22 @@ EOF
   [ "$status" -eq 0 ]
   [ "$output" = "$message" ]
 }
+
+@test "with_shim_executable doesn't crash when executable names contain plusses" {
+  cd "$PROJECT_DIR"
+  echo "dummy 0.1.0" >"$PROJECT_DIR/.tool-versions"
+  mkdir -p "$ASDF_DIR/installs/dummy/0.1.0/bin"
+  touch "$ASDF_DIR/installs/dummy/0.1.0/bin/test++"
+  chmod +x "$ASDF_DIR/installs/dummy/0.1.0/bin/test++"
+  run asdf reshim dummy 0.1.0
+
+  message="callback invoked"
+
+  callback() {
+    echo "$message"
+  }
+
+  run with_shim_executable test++ callback
+  [ "$status" -eq 0 ]
+  [ "$output" = "$message" ]
+}