Ask cmake to find git executable

Related work item: Github #28

External/CMakeLists.txt

@@ -1,6 +1,11 @@
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License.
 
+find_program(git_executable NAMES git git.exe git.cmd)
+if(NOT git_executable)
+    message(FATAL_ERROR "Failed to find git.")
+endif()
+
 set(cxxopts_REV "3f2d70530219e09fe7e563f86126b0d3b228a60d")
 set(googletest_REV "440527a61e1c91188195f7de212c63c77e8f0a45")
 set(SPIRV_Headers_REV "bbf63435c37aafac5d1cdfc287401d87cd3ca364")
@@ -14,8 +19,8 @@ function(UpdateExternalLib name url rev)
     set(external_lib_folder "${external_folder}/${name}")
     if(EXISTS ${external_lib_folder})
         message(STATUS "Updating ${name} to revision ${rev}...")
-        execute_process(COMMAND "git" "fetch" "origin" WORKING_DIRECTORY "${external_lib_folder}")
+        execute_process(COMMAND "${git_executable}" "fetch" "origin" WORKING_DIRECTORY "${external_lib_folder}")
-        execute_process(COMMAND "git" "rev-parse" "HEAD" WORKING_DIRECTORY "${external_lib_folder}" OUTPUT_VARIABLE head_rev)
+        execute_process(COMMAND "${git_executable}" "rev-parse" "HEAD" WORKING_DIRECTORY "${external_lib_folder}" OUTPUT_VARIABLE head_rev)
         string(STRIP ${head_rev} head_rev)
         if (${head_rev} STREQUAL ${rev})
             set(need_checkout FALSE)
@@ -24,12 +29,12 @@ function(UpdateExternalLib name url rev)
         endif()
     else()
         message(STATUS "Cloning ${name} revision...")
-        execute_process(COMMAND "git" "clone" ${url} "-n" WORKING_DIRECTORY "${external_folder}")
+        execute_process(COMMAND "${git_executable}" "clone" ${url} "-n" WORKING_DIRECTORY "${external_folder}")
         set(need_checkout TRUE)
     endif()
     if(need_checkout)
         message(STATUS "Checking out to revision ${rev}...")
-        execute_process(COMMAND "git" "checkout" "-q" ${rev} WORKING_DIRECTORY "${external_lib_folder}")
+        execute_process(COMMAND "${git_executable}" "checkout" "-q" ${rev} WORKING_DIRECTORY "${external_lib_folder}")
     endif()
 endfunction()
 

README.md

@@ -26,7 +26,7 @@ ShaderConductor is not a real compiler. Instead, it glues existing open source c
 
 ## Prerequisites
 
-* [Git](http://git-scm.com/downloads).
+* [Git](http://git-scm.com/downloads). Put git into the PATH is recommended.
 * [Visual Studio 2017](https://www.visualstudio.com/downloads). Select the following workloads: Universal Windows Platform Development and Desktop Development with C++.
 * [CMake](https://www.cmake.org/download/). Version 3.9 or up. It's highly recommended to choose "Add CMake to the system PATH for all users" during installation.
 * [Python](https://www.python.org/downloads/). Version 2.7 or up. You need not change your PATH variable during installation.