cmake: get version from git ref

cmake/GetGitVersion.cmake

@@ -0,0 +1,47 @@
+find_package(Git)
+
+function(get_git_version var1 var2)
+  if(GIT_EXECUTABLE)
+    execute_process(
+      COMMAND ${GIT_EXECUTABLE} describe --tags --match "[0-9]*.[0-9]*.[0-9]*" --abbrev=8
+      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+      RESULT_VARIABLE status
+      OUTPUT_VARIABLE GIT_VERSION
+    )
+    if (${status})
+      set(GIT_VERSION "0.0.0")
+    else()
+      string(STRIP ${GIT_VERSION} GIT_VERSION)
+      string(REGEX REPLACE "-[0-9]+-g" "-" GIT_VERSION ${GIT_VERSION})
+    endif()
+  else()
+    set(GIT_VERSION "0.0.0")
+  endif()
+
+  string(REGEX MATCH "^[0-9]+.[0-9]+.[0-9]+" SEM_VER "${GIT_VERSION}")
+
+  message("-- Git Tag: ${GIT_VERSION}, Sem Ver: ${SEM_VER}")
+
+  set(${var1} ${GIT_VERSION} PARENT_SCOPE)
+  set(${var2} ${SEM_VER} PARENT_SCOPE)
+endfunction()
+
+function(get_git_head var1)
+  if(GIT_EXECUTABLE)
+    execute_process(
+      COMMAND ${GIT_EXECUTABLE} --git-dir ${CMAKE_CURRENT_SOURCE_DIR}/.git rev-parse --short HEAD
+      RESULT_VARIABLE status
+      OUTPUT_VARIABLE GIT_COMMIT
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+      ERROR_QUIET
+    )
+
+    if(${status})
+      set(GIT_COMMIT "unknown")
+    endif()
+
+    message("-- Git Commit: ${GIT_COMMIT}")
+
+    set(${var1} ${GIT_COMMIT} PARENT_SCOPE)
+  endif()
+endfunction()