From 733b50e9aee391c41c89fffae8541dc901aaf16e Mon Sep 17 00:00:00 2001
From: valentink-eroad <82477839+valentink-eroad@users.noreply.github.com>
Date: Thu, 14 Apr 2022 20:15:40 +1200
Subject: [PATCH] CMake: add a flag to enable version lookup outside the root
 folder (#533)

Add ARGN to determine_version_with_git() parameters list to allow
specifying the optional ALLOW_LOOKING_ABOVE_CMAKE_SOURCE_DIR flag
---
 CMakeLists.txt                        | 2 +-
 README.md                             | 7 +++++++
 cmake/GetGitRevisionDescription.cmake | 2 +-
 cmake/helpers.cmake                   | 2 +-
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 30396eef..4ffc37b3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,7 +5,7 @@ cmake_minimum_required(VERSION 3.5.0)
 
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/helpers.cmake)
 
-determine_version_with_git()
+determine_version_with_git(${GIT_DIR_LOOKUP_POLICY})
 
 project(etl VERSION ${ETL_VERSION})
 
diff --git a/README.md b/README.md
index d36ecc3c..72601b2c 100644
--- a/README.md
+++ b/README.md
@@ -77,6 +77,13 @@ add_executable(foo main.cpp)
 target_link_libraries(foo PRIVATE etl)
 ```
 
+If ETL library is used as a Git submodule it may require additional configuration for proper ETL version resolution by allowing the lookup for Git folder outside of the library root directory.
+
+```cmake
+set(GIT_DIR_LOOKUP_POLICY ALLOW_LOOKING_ABOVE_CMAKE_SOURCE_DIR)
+add_subdirectory(etl)
+```
+
 If you want to install this library with CMake, you can perform the following steps. On Linux,
 super user rights might be required to install the library, so it might be necessary to add
 `sudo` before the last command:
diff --git a/cmake/GetGitRevisionDescription.cmake b/cmake/GetGitRevisionDescription.cmake
index 4fbd90db..0a203502 100644
--- a/cmake/GetGitRevisionDescription.cmake
+++ b/cmake/GetGitRevisionDescription.cmake
@@ -176,7 +176,7 @@ function(git_describe _var)
     if(NOT GIT_FOUND)
         find_package(Git QUIET)
     endif()
-    get_git_head_revision(refspec hash)
+    get_git_head_revision(refspec hash ${ARGN})
     if(NOT GIT_FOUND)
         set(${_var}
             "GIT-NOTFOUND"
diff --git a/cmake/helpers.cmake b/cmake/helpers.cmake
index d339cae8..72e6017e 100644
--- a/cmake/helpers.cmake
+++ b/cmake/helpers.cmake
@@ -10,7 +10,7 @@ endfunction()
 
 function(determine_version_with_git)
     include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/GetGitRevisionDescription.cmake)
-    git_describe(VERSION)
+    git_describe(VERSION ${ARGN})
     string(FIND ${VERSION} "." VALID_VERSION)
     if(VALID_VERSION EQUAL -1)
         message(WARNING "Version string ${VERSION} retrieved with git describe is invalid")