Add core storage plugin to manage docker bind mounts [ci skip]

plugins/storage/functions

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+
+verify_paths() {
+  echo "$1" | grep -qe '^/.*\:/' || dokku_log_fail "Storage path must be two valid paths devided by colon."
+}
+
+check_if_path_exists() {
+  local -r passed_path=$1
+  local -r phase_file_path=$2
+  [[ -r "$phase_file_path" ]] && grep -qe "^-v $passed_path" "$phase_file_path"
+}
+
+get_bind_mounts() {
+  local -r phase_file_path=$1
+  [[ -r "$phase_file_path" ]] && sed -e '/^-v/!d' -e 's/^-v/    /' < "$phase_file_path"
+}