Revert "Remove git based support for testing examples" (cpp-pm#170)

This reverts commit 7312c58.

examples/common.cmake

@@ -1,7 +1,7 @@
-# Copyright (c) 2013, 2015, 2019 Ruslan Baratov
+# Copyright (c) 2013, 2015 Ruslan Baratov
 # All rights reserved.
 
-cmake_minimum_required(VERSION 3.2)
+cmake_minimum_required(VERSION 3.0)
 
 ### Include HunterGate module from git submodule
 set(gate_dir "${CMAKE_CURRENT_LIST_DIR}/../gate")
@@ -18,27 +18,17 @@ endif()
 message("Including HunterGate: ${gate_module}")
 include("${gate_module}")
 
-set(
-    error_message
-    "Are you using jenkins.py script for testing?
-    Please check:
-    - https://hunter.readthedocs.io/en/latest/creating-new/create/cmake.html#testing-locally"
-)
-
 ### Check testing variables are set
-if("${TESTING_URL}" STREQUAL "")
-  message(FATAL_ERROR "TESTING_URL is empty. ${error_message}")
-endif()
-
-if("${TESTING_SHA1}" STREQUAL "")
-  message(FATAL_ERROR "TESTING_SHA1 is empty. ${error_message}")
+string(COMPARE EQUAL "${TESTING_URL}" "" url_is_empty)
+string(COMPARE EQUAL "${TESTING_SHA1}" "" sha1_is_empty)
+string(COMPARE EQUAL "${HUNTER_ROOT}" "" hunter_root_is_empty)
+
+if(NOT url_is_empty AND NOT sha1_is_empty AND NOT hunter_root_is_empty)
+  get_filename_component(TESTING_URL "${TESTING_URL}" ABSOLUTE)
+
+  ### HunterGate module
+  HunterGate(URL "${TESTING_URL}" SHA1 "${TESTING_SHA1}" ${TESTING_CONFIG_OPT})
+else()
+  get_filename_component(HUNTER_ROOT "${CMAKE_CURRENT_LIST_DIR}/.." ABSOLUTE)
+  HunterGate(URL "x" SHA1 "xxxxxxxx" ${TESTING_CONFIG_OPT})
 endif()
-
-if("${HUNTER_ROOT}" STREQUAL "")
-  message(FATAL_ERROR "HUNTER_ROOT is empty. ${error_message}")
-endif()
-
-get_filename_component(TESTING_URL "${TESTING_URL}" ABSOLUTE)
-
-### HunterGate module
-HunterGate(URL "${TESTING_URL}" SHA1 "${TESTING_SHA1}" ${TESTING_CONFIG_OPT})