trying to add support for generating version info from git (does not work yet)

cmake/version.cmake

@@ -0,0 +1,43 @@
+execute_process(COMMAND git log --pretty=format:'%h' -n 1
+	OUTPUT_VARIABLE GIT_REV
+	ERROR_QUIET)
+
+# Check whether we got any revision (which isn't
+# always the case, e.g. when someone downloaded a zip
+# file from Github instead of a checkout)
+if ("${GIT_REV}" STREQUAL "")
+	set(GIT_REV "N/A")
+	set(GIT_DIFF "")
+	set(GIT_TAG "N/A")
+	set(GIT_BRANCH "N/A")
+else()
+	execute_process(
+        COMMAND bash -c "git diff --quiet --exit-code || echo +"
+        OUTPUT_VARIABLE GIT_DIFF)
+    execute_process(
+        COMMAND git describe --exact-match --tags
+        OUTPUT_VARIABLE GIT_TAG ERROR_QUIET)
+    execute_process(
+        COMMAND git rev-parse --abbrev-ref HEAD
+        OUTPUT_VARIABLE GIT_BRANCH)
+
+    string(STRIP "${GIT_REV}" GIT_REV)
+    string(SUBSTRING "${GIT_REV}" 1 7 GIT_REV)
+    string(STRIP "${GIT_DIFF}" GIT_DIFF)
+    string(STRIP "${GIT_TAG}" GIT_TAG)
+    string(STRIP "${GIT_BRANCH}" GIT_BRANCH)
+endif()
+
+set(VERSION "const char* GIT_REV=\"${GIT_REV}${GIT_DIFF}\";
+const char* GIT_TAG=\"${GIT_TAG}\";
+const char* GIT_BRANCH=\"${GIT_BRANCH}\";")
+
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/version.cpp)
+    file(READ ${CMAKE_CURRENT_SOURCE_DIR}/version.cpp VERSION_)
+else()
+    set(VERSION_ "")
+endif()
+
+if (NOT "${VERSION}" STREQUAL "${VERSION_}")
+    file(WRITE ${CMAKE_CURRENT_SOURCE_DIR}/version.cpp "${VERSION}")
+endif()