Prepare build for Git repository

This includes fetching the build revision from git instead of hg
and adding a file to store the revision hash in archives.

.git_archival

@@ -0,0 +1 @@
+node: $Format:%H$

.gitattributes

@@ -0,0 +1,3 @@
+.git_archival	export-subst
+.gitattributes	export-ignore
+.gitignore	export-ignore

.gitignore

@@ -1,5 +1,3 @@
-syntax: glob
-
 autom4te.cache
 *~
 *.bak

.hgeol

@@ -1,3 +0,0 @@
-[patterns]
-planet/** = LF
-** = native

Version.txt

@@ -22,22 +22,10 @@ SET(C4VERSIONBUILDNAME  " Beyond the Rocks")
 SET(C4VERSIONEXTRA      " Delta")
 
 ############################################################################
-# Get revision from Mercurial
+# Get revision from Git
 ############################################################################
-if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.hg_archival.txt")
-	# Archives generated by hg archive
-	file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/.hg_archival.txt" C4REVISION
-		LIMIT_COUNT 1
-		REGEX "node: [0-9a-f]+"
-	)
-	string(SUBSTRING "${C4REVISION}" 6 12 C4REVISION)
-else()
-	# Working copies
-	execute_process(WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
-		COMMAND "hg" "id" "--id"
-		OUTPUT_VARIABLE C4REVISION
-		OUTPUT_STRIP_TRAILING_WHITESPACE)
-endif()
+include(GitGetChangesetID)
+git_get_changeset_id(C4REVISION)
 
 ############################################################################
 # Get year

cmake/GitGetChangesetID.cmake

@@ -0,0 +1,32 @@
+function(git_get_changeset_id VAR)
+	find_package(Git QUIET)
+	if (GIT_FOUND)
+		execute_process(WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+			COMMAND "${GIT_EXECUTABLE}" "rev-parse" "HEAD"
+			RESULT_VARIABLE GIT_RESULT
+			OUTPUT_VARIABLE C4REVISION
+			OUTPUT_STRIP_TRAILING_WHITESPACE
+			ERROR_QUIET)
+
+		if(GIT_RESULT EQUAL 0)
+			string(SUBSTRING "${C4REVISION}" 0 12 C4REVISION)
+			execute_process(WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+				COMMAND "${GIT_EXECUTABLE}" "status" "--porcelain"
+				OUTPUT_VARIABLE GIT_STATUS
+			)
+			string(REGEX MATCH "^[MADRC ][MD ]" WORKDIR_DIRTY "${GIT_STATUS}")
+		endif()
+	endif()
+	if (NOT C4REVISION)
+		# Git not found or not a git workdir
+		file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/.git_archival" C4REVISION
+			LIMIT_COUNT 1
+			REGEX "node: [0-9a-f]+"
+		)
+		string(SUBSTRING "${C4REVISION}" 6 12 C4REVISION)
+	endif()
+	if(WORKDIR_DIRTY)
+		set(C4REVISION "${C4REVISION}+")
+	endif()
+	set(${VAR} "${C4REVISION}" PARENT_SCOPE)
+endfunction()