From 9ed415ad43d4625ebb92ac1b800e57064e65aebc Mon Sep 17 00:00:00 2001
From: Ben Boeckel <ben.boeckel@kitware.com>
Date: Tue, 21 Oct 2014 14:03:54 -0400
Subject: [PATCH] build: inform the build of what generates version.h

Without this, Ninja requires a two-step process because it doesn't know
what generates version.h it sees from its depfile support and when it
changes in one run, it has already pruned the dependent nodes from its
internal graph and requires a second run to catch it.
---
 version.cmake | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/version.cmake b/version.cmake
index 4dd6db6d..80f1c40b 100644
--- a/version.cmake
+++ b/version.cmake
@@ -11,12 +11,22 @@ if ("$Format:$" STREQUAL "")
   write_static_version_header("release")
 elseif (GIT_FOUND OR Git_FOUND)
   message(STATUS "Found Git: ${GIT_EXECUTABLE}")
-  add_custom_target(version ALL
+  set(extra_output)
+  if (CMAKE_GENERATOR MATCHES "Ninja")
+    # Ninja will not rerun the command every time if the file doesn't change,
+    # so inject this bogus output so that it always runs.
+    set(extra_output "${CMAKE_SOURCE_DIR}/.force-git-version-check")
+  endif ()
+  add_custom_command(
+    OUTPUT            "${CMAKE_BINARY_DIR}/version/version.h"
+                      ${extra_output}
     COMMAND           "${CMAKE_COMMAND}"
                       "-D" "GIT=${GIT_EXECUTABLE}"
                       "-D" "TO=${CMAKE_BINARY_DIR}/version/version.h"
                       "-P" "src/version.cmake"
     WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}")
+  add_custom_target(version ALL
+    DEPENDS "${CMAKE_BINARY_DIR}/version/version.h")
 else()
   message(STATUS "WARNING: Git was not found!")
   write_static_version_header("unknown")