1 files changed, 71 insertions, 0 deletions
diff --git a/cmake/ExternalProjectFlags.cmake b/cmake/ExternalProjectFlags.cmake
new file mode 100644
index 0000000..ed4db2c
--- /dev/null
+++ b/cmake/ExternalProjectFlags.cmake
@@ -0,0 +1,71 @@
+# Copyright 2018 Google
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+include(CMakeParseArguments)
+
+# Assemble the git-related arguments to an external project making use of the
+# latest features where available but avoiding them when run under CMake
+# versions that don't support them.
+#
+# The complete set of git-related arguments are stored as a list in the
+# variable named by RESULT_VAR in the calling scope.
+#
+# Currently this handles:
+#   * GIT_SUBMODULES -- added on CMake 3.0 or later. Earlier CMakes will
+#       check out all submodules.
+#   * GIT_SHALLOW -- added by default on CMake 3.6 or later. Disable by passing
+#       GIT_SHALLOW OFF
+#   * GIT_PROGRESS -- added by default on CMake 3.8 or later. Disable by
+#       passing GIT_PROGRESS OFF
+function(ExternalProject_GitSource RESULT_VAR)
+  # Parse arguments
+  set(options "")
+  set(single_value GIT_REPOSITORY GIT_TAG GIT_PROGRESS GIT_SHALLOW)
+  set(multi_value GIT_SUBMODULES)
+  cmake_parse_arguments(EP "${options}" "${single_value}" "${multi_value}" ${ARGN})
+
+  set(
+    result
+    GIT_REPOSITORY ${EP_GIT_REPOSITORY}
+    GIT_TAG ${EP_GIT_TAG}
+    ${EP_UNPARSED_ARGUMENTS}
+  )
+
+  # CMake 3.0 added support for constraining the set of submodules to clone
+  if(NOT (CMAKE_VERSION VERSION_LESS "3.0") AND EP_GIT_SUBMODULES)
+    list(APPEND result GIT_SUBMODULES ${EP_GIT_SUBMODULES})
+  endif()
+
+  # CMake 3.6 added support for shallow git clones. Use a shallow clone if
+  # available
+  if(NOT (CMAKE_VERSION VERSION_LESS "3.6"))
+    if(NOT EP_GIT_SHALLOW)
+      set(EP_GIT_SHALLOW ON)
+    endif()
+
+    list(APPEND result GIT_SHALLOW ${EP_GIT_SHALLOW})
+  endif()
+
+  # CMake 3.8 added support for showing progress for large downloads
+  if(NOT (CMAKE_VERSION VERSION_LESS "3.8"))
+    if(NOT EP_GIT_PROGRESS)
+      set(EP_GIT_PROGRESS ON)
+    endif()
+
+    list(APPEND result GIT_PROGRESS ${EP_GIT_PROGRESS})
+  endif()
+
+  set(${RESULT_VAR} ${result} PARENT_SCOPE)
+
+endfunction()