message: Allow external overriding of auto-fetched git hash identifier in cmake
  * This is useful if the build doesn't happen within a git checkout and
  you want to pass in the hash anyway, but it also allows adding
  suffixes like -official etc.
diff: @@ -29,6 +29,8 @@ if(CMAKE_BINARY_DIR STREQUAL CMAKE_SOURCE_DIR)
  message(FATAL_ERROR "In-source builds not allowed")
  endif()
  +set(BUILD_VERSION_HASH "" CACHE STRING "The current git commit hash, possibly with suffixes to indicate build type")
  +
  function(get_git_hash _git_hash)
  if(EXISTS "${CMAKE_SOURCE_DIR}/.git")
  execute_process(
  @@ -41,6 +43,9 @@ function(get_git_hash _git_hash)
  if(NOT GIT_HASH)
  set(GIT_HASH "NO_GIT_COMMIT_HASH_DEFINED")
  endif()
  + if(BUILD_VERSION_HASH)
  + set(GIT_HASH "${BUILD_VERSION_HASH}")
  + endif()
  set(${_git_hash} "${GIT_HASH}" PARENT_SCOPE)
  endfunction(get_git_hash)
  