- Change updaterevision to a CMake script

The benefit to this is fairly small, but it does mean a little less work needs
to be done in the build scripts for cross compiling. The C version wasn't
especially concise so it was not obviously better in any way.

src/CMakeLists.txt

@@ -426,9 +426,9 @@ endif()
 # Update gitinfo.h
 
 add_custom_target( revision_check ALL
-	COMMAND updaterevision src/gitinfo.h
+	COMMAND "${CMAKE_COMMAND}" -P "${CMAKE_SOURCE_DIR}/tools/updaterevision/UpdateRevision.cmake" src/gitinfo.h
 	WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
-	DEPENDS updaterevision )
+)
 
 # Libraries ZDoom needs
 

tools/CMakeLists.txt

@@ -2,7 +2,6 @@ cmake_minimum_required( VERSION 2.8.7 )
 
 add_subdirectory( re2c )
 add_subdirectory( lemon )
-add_subdirectory( updaterevision )
 add_subdirectory( zipdir )
 
 set( CROSS_EXPORTS ${CROSS_EXPORTS} PARENT_SCOPE )

tools/updaterevision/UpdateRevision.cmake

@@ -0,0 +1,91 @@
+#!/usr/bin/cmake -P
+
+# UpdateRevision.cmake
+#
+# Public domain. This program uses git commands command to get
+# various bits of repository status for a particular directory
+# and writes it into a header file so that it can be used for a
+# project's versioning.
+
+# Boilerplate to return a variable from a function.
+macro(ret_var VAR)
+	set(${VAR} "${${VAR}}" PARENT_SCOPE)
+endmacro()
+
+# Populate variables "Hash", "Tag", and "Timestamp" with relevant information
+# from source repository.  If anything goes wrong return something in "Error."
+function(query_repo_info)
+	execute_process(
+		COMMAND git describe --tags --dirty=-m
+		RESULT_VARIABLE Error
+		OUTPUT_VARIABLE Tag
+		ERROR_QUIET
+		OUTPUT_STRIP_TRAILING_WHITESPACE
+	)
+	if(NOT "${Error}" STREQUAL "0")
+		ret_var(Error)
+		return()
+	endif()
+
+	execute_process(
+		COMMAND git log -1 "--format=%ai;%H"
+		RESULT_VARIABLE Error
+		OUTPUT_VARIABLE CommitInfo
+		ERROR_QUIET
+		OUTPUT_STRIP_TRAILING_WHITESPACE
+	)
+	if(NOT "${Error}" STREQUAL "0")
+		ret_var(Error)
+		return()
+	endif()
+
+	list(GET CommitInfo 0 Timestamp)
+	list(GET CommitInfo 1 Hash)
+
+	ret_var(Tag)
+	ret_var(Timestamp)
+	ret_var(Hash)
+endfunction()
+
+# Although configure_file doesn't overwrite the file if the contents are the
+# same we can't easily observe that to change the status message.  This
+# function parses the existing file (if it exists) and puts the hash in
+# variable "OldHash"
+function(get_existing_hash File)
+	if(EXISTS "${File}")
+		file(STRINGS "${File}" OldHash LIMIT_COUNT 1)
+		if(OldHash)
+			string(SUBSTRING "${OldHash}" 3 -1 OldHash)
+			ret_var(OldHash)
+		endif()
+	endif()
+endfunction()
+
+function(main)
+	if(NOT CMAKE_ARGC EQUAL 4) # cmake -P UpdateRevision.cmake <OutputFile>
+		message("Usage: ${CMAKE_ARGV2} <path to gitinfo.h>")
+		return()
+	endif()
+	set(OutputFile "${CMAKE_ARGV3}")
+
+	get_filename_component(ScriptDir "${CMAKE_SCRIPT_MODE_FILE}" DIRECTORY)
+
+	query_repo_info()
+	if(NOT Hash)
+		message("Failed to get commit info: ${Error}")
+		set(Hash "0")
+		set(Tag "<unknown version>")
+		set(Timestamp "")
+	endif()
+
+	get_existing_hash("${OutputFile}")
+	if(Hash STREQUAL OldHash)
+		message("${OutputFile} is up to date at commit ${Tag}.")
+		return()
+	endif()
+
+	configure_file("${ScriptDir}/gitinfo.h.in" "${OutputFile}")
+	message("${OutputFile} updated to commit ${Tag}.")
+endfunction()
+
+main()

tools/updaterevision/gitinfo.h.in

@@ -0,0 +1,8 @@
+// @Hash@
+//
+// This file was automatically generated by the
+// updaterevision tool. Do not edit by hand.
+
+#define GIT_DESCRIPTION "@Tag@"
+#define GIT_HASH "@Hash@"
+#define GIT_TIME "@Timestamp@"