diff --git a/binaries/data/config/dev.cfg b/binaries/data/config/dev.cfg
new file mode 100644
index 0000000000..ef3e5be923
--- /dev/null
+++ b/binaries/data/config/dev.cfg
@@ -0,0 +1,11 @@
+;
+; Developer configuration file
+;
+; NOTE: This is not read by the config system currently.
+;
+; This file is used by the engine to decide which mods are mounted, and in what
+; order. The precense of this file suppresses loading of mods in the user mod
+; path (see http://trac.wildfiregames.com/wiki/GameDataPaths) if the same mod is
+; present in binaries/data/mods. It also implies -noUserMod.
+; This is done to make saved maps end up in the right mod folder (and in the 
+; game-relative data path) to commit them later on. 
diff --git a/build/workspaces/build-osx-bundle.sh b/build/workspaces/build-osx-bundle.sh
index 3f861d5cb0..ae09be7aee 100755
--- a/build/workspaces/build-osx-bundle.sh
+++ b/build/workspaces/build-osx-bundle.sh
@@ -158,9 +158,13 @@ cp -v ../../binaries/system/libCollada.dylib ${BUNDLE_FRAMEWORKS}
 
 # Copy data
 echo "\nCopying non-archived game data\n"
+# Removing it now and restoring it later, cp has no exclusion switch
+# and using find is a bit over-the-top
+rm ../../binaries/data/config/dev.cfg
 cp -v ../resources/0ad.icns ${BUNDLE_RESOURCES}
 cp -R -v ../../binaries/data/config ${BUNDLE_RESOURCES}/data/
 cp -R -v ../../binaries/data/tools ${BUNDLE_RESOURCES}/data/
+svn revert ../../binaries/data/config/dev.cfg
 
 # Copy license/readmes
 # TODO: Also want copies in the DMG - decide on layout
diff --git a/source/lib/file/vfs/vfs.cpp b/source/lib/file/vfs/vfs.cpp
index 8a609f8f20..b0551c7a3e 100644
--- a/source/lib/file/vfs/vfs.cpp
+++ b/source/lib/file/vfs/vfs.cpp
@@ -132,7 +132,7 @@ public:
 	{
 		ScopedLock s;
 		VfsDirectory* directory;
-		WARN_RETURN_STATUS_IF_ERR(vfs_Lookup(pathname, &m_rootDirectory, directory, 0, VFS_LOOKUP_ADD|VFS_LOOKUP_CREATE));
+		WARN_RETURN_STATUS_IF_ERR(vfs_Lookup(pathname, &m_rootDirectory, directory, 0, VFS_LOOKUP_ADD|VFS_LOOKUP_CREATE|VFS_LOOKUP_CREATE_ALWAYS));
 
 		const PRealDirectory& realDirectory = directory->AssociatedDirectory();
 		const OsPath name = pathname.Filename();
diff --git a/source/lib/file/vfs/vfs.h b/source/lib/file/vfs/vfs.h
index fcf10037e9..e038c5b48d 100644
--- a/source/lib/file/vfs/vfs.h
+++ b/source/lib/file/vfs/vfs.h
@@ -65,7 +65,16 @@ enum VfsMountFlags
 	 * ".DELETED" suffix will still apply.
 	 * (the default behavior is to hide both the suffixed and unsuffixed files)
 	 **/
-	VFS_MOUNT_KEEP_DELETED = 8
+	VFS_MOUNT_KEEP_DELETED = 8,
+
+	/**
+	 * mark a directory replaceable, so that when writing a file to this path
+	 * new real directories will be created instead of reusing already existing
+	 * ones mounted at a subpath of the VFS path.
+	 * (the default behaviour is to write to the real directory associated
+	 * with the VFS directory that was last mounted to this path (or subpath))
+	 **/
+	VFS_MOUNT_REPLACEABLE = 16
 };
 
 // (member functions are thread-safe after the instance has been
diff --git a/source/lib/file/vfs/vfs_lookup.cpp b/source/lib/file/vfs/vfs_lookup.cpp
index fb7ba52f8a..5c99ea73e6 100644
--- a/source/lib/file/vfs/vfs_lookup.cpp
+++ b/source/lib/file/vfs/vfs_lookup.cpp
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010 Wildfire Games
+/* Copyright (c) 2013 Wildfire Games
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -74,7 +74,8 @@ Status vfs_Lookup(const VfsPath& pathname, VfsDirectory* startDirectory, VfsDire
 	const bool addMissingDirectories    = (flags & VFS_LOOKUP_ADD) != 0;
 	const bool createMissingDirectories = (flags & VFS_LOOKUP_CREATE) != 0;
 	const bool skipPopulate = (flags & VFS_LOOKUP_SKIP_POPULATE) != 0;
-	ENSURE((flags & ~(VFS_LOOKUP_ADD|VFS_LOOKUP_CREATE|VFS_LOOKUP_SKIP_POPULATE)) == 0);
+	const bool createAlways = (flags & VFS_LOOKUP_CREATE_ALWAYS) != 0;
+	ENSURE((flags & ~(VFS_LOOKUP_ADD|VFS_LOOKUP_CREATE|VFS_LOOKUP_SKIP_POPULATE|VFS_LOOKUP_CREATE_ALWAYS)) == 0);
 
 	directory = startDirectory;
 	if(pfile)
@@ -111,7 +112,8 @@ Status vfs_Lookup(const VfsPath& pathname, VfsDirectory* startDirectory, VfsDire
 				return ERR::VFS_DIR_NOT_FOUND;	// NOWARN
 		}
 
-		if(createMissingDirectories && !subdirectory->AssociatedDirectory())
+		if(createMissingDirectories && (!subdirectory->AssociatedDirectory()
+		     || (createAlways && (subdirectory->AssociatedDirectory()->Flags() & VFS_MOUNT_REPLACEABLE) != 0)))
 		{
 			OsPath currentPath;
 			if(directory->AssociatedDirectory())	// (is NULL when mounting into root)
diff --git a/source/lib/file/vfs/vfs_lookup.h b/source/lib/file/vfs/vfs_lookup.h
index 3a369a378c..733eb599e2 100644
--- a/source/lib/file/vfs/vfs_lookup.h
+++ b/source/lib/file/vfs/vfs_lookup.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010 Wildfire Games
+/* Copyright (c) 2013 Wildfire Games
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -49,7 +49,12 @@ enum VfsLookupFlags
 	// don't populate the directories encountered. this makes sense
 	// when adding files from an archive, which would otherwise
 	// cause nearly every directory to be populated.
-	VFS_LOOKUP_SKIP_POPULATE = 4
+	VFS_LOOKUP_SKIP_POPULATE = 4,
+
+	// even create directories if they are already present, this is
+	// useful to write new files to the directory that was attached
+	// last, if the directory wasn't mounted with VFS_MOUNT_REPLACEABLE
+	VFS_LOOKUP_CREATE_ALWAYS = 8
 };
 
 /**
diff --git a/source/ps/GameSetup/GameSetup.cpp b/source/ps/GameSetup/GameSetup.cpp
index 5744e8ba76..b5e551eca5 100644
--- a/source/ps/GameSetup/GameSetup.cpp
+++ b/source/ps/GameSetup/GameSetup.cpp
@@ -421,6 +421,20 @@ ErrorReactionInternal psDisplayError(const wchar_t* UNUSED(text), size_t UNUSED(
 	return ERI_NOT_IMPLEMENTED;
 }
 
+static std::vector<CStr> GetMods(const CmdLineArgs& args, bool dev)
+{
+	std::vector<CStr> mods = args.GetMultiple("mod");
+	// TODO: It would be nice to remove this hard-coding
+	mods.insert(mods.begin(), "public");
+
+	// Add the user mod if not explicitly disabled or we have a dev copy so
+	// that saved files end up in version control and not in the user mod.
+	if (!dev && !args.Has("noUserMod"))
+		mods.push_back("user");
+
+	return mods;
+}
+
 static void InitVfs(const CmdLineArgs& args)
 {
 	TIMER(L"InitVfs");
@@ -441,28 +455,44 @@ static void InitVfs(const CmdLineArgs& args)
 
 	const size_t cacheSize = ChooseCacheSize();
 	g_VFS = CreateVfs(cacheSize);
+	
+	// Work out whether we are a dev version to make sure saved files
+	// (maps, etc) end up in version control.
+	const OsPath readonlyConfig = paths.RData()/"config"/"";
+	g_VFS->Mount(L"config/", readonlyConfig);
+	bool dev = (g_VFS->GetFileInfo(L"config/dev.cfg", NULL) == INFO::OK);
 
-	std::vector<CStr> mods = args.GetMultiple("mod");
-	mods.insert(mods.begin(), "public");
-
-	if (!args.Has("noUserMod"))
-		mods.push_back("user");
+	const std::vector<CStr> mods = GetMods(args, dev);
 
 	OsPath modPath = paths.RData()/"mods";
 	OsPath modUserPath = paths.UserData()/"mods";
 	for (size_t i = 0; i < mods.size(); ++i)
 	{
-		size_t priority = i+1;	// mods are higher priority than regular mountings, which default to priority 0
-		size_t flags = VFS_MOUNT_WATCH|VFS_MOUNT_ARCHIVABLE|VFS_MOUNT_MUST_EXIST;
+		size_t priority = (i+1)*2;	// mods are higher priority than regular mountings, which default to priority 0
+		size_t userFlags = VFS_MOUNT_WATCH|VFS_MOUNT_ARCHIVABLE|VFS_MOUNT_REPLACEABLE;
+		size_t flags = userFlags|VFS_MOUNT_MUST_EXIST;
+		
 		OsPath modName(mods[i]);
-		g_VFS->Mount(L"", modPath / modName/"", flags, priority);
-		g_VFS->Mount(L"", modUserPath / modName/"", flags, priority);
+		if (dev)
+		{
+			// We are running a dev copy, so only mount mods in the user mod path
+			// if the mod does not exist in the data path.
+			if (DirectoryExists(modPath / modName/""))
+				g_VFS->Mount(L"", modPath / modName/"", flags, priority);
+			else
+				g_VFS->Mount(L"", modUserPath / modName/"", userFlags, priority);
+		}
+		else
+		{
+			g_VFS->Mount(L"", modPath / modName/"", flags, priority);
+			// Ensure that user modified files are loaded, if they are present
+			g_VFS->Mount(L"", modUserPath / modName/"", userFlags, priority+1);
+		}
 	}
 
 	// We mount these dirs last as otherwise writing could result in files being placed in a mod's dir.
 	g_VFS->Mount(L"screenshots/", paths.UserData()/"screenshots"/"");
 	g_VFS->Mount(L"saves/", paths.UserData()/"saves"/"", VFS_MOUNT_WATCH);
-	const OsPath readonlyConfig = paths.RData()/"config"/"";
 	// Mounting with highest priority, so that a mod supplied user.cfg is harmless
 	g_VFS->Mount(L"config/", readonlyConfig, 0, (size_t)-1);
 	if(readonlyConfig != paths.Config())
@@ -889,13 +919,13 @@ void Init(const CmdLineArgs& args, int UNUSED(flags))
 
 	// g_ConfigDB, command line args, globals
 	CONFIG_Init(args);
-	
+
 	// before scripting 
 	if (g_JSDebuggerEnabled)
 		g_DebuggingServer = new CDebuggingServer();
 
 	InitScripting();	// before GUI
-	
+
 	g_ConfigDB.RegisterJSConfigDB(); 	// after scripting 
 
 	// Optionally start profiler HTTP output automatically
diff --git a/source/tools/dist/build.sh b/source/tools/dist/build.sh
index e9345270c5..8966f35535 100755
--- a/source/tools/dist/build.sh
+++ b/source/tools/dist/build.sh
@@ -39,7 +39,9 @@ tar cf $PREFIX-unix-build.tar \
 	--exclude='libraries/source/fcollada/src/FCollada/FColladaTest' \
 	--exclude='libraries/source/spidermonkey/include-win32' \
 	${PREFIX}/{source,build,libraries/source,binaries/system/readme.txt,binaries/data/tests,binaries/data/mods/_test.*,*.txt}
-tar cf $PREFIX-unix-data.tar ${PREFIX}/binaries/data/{config,mods/public/public.zip,tools}
+tar cf $PREFIX-unix-data.tar \
+	--exclude='binaries/data/config/dev.cfg' \
+	 ${PREFIX}/binaries/data/{config,mods/public/public.zip,tools}
 # TODO: ought to include generated docs in here, perhaps?
 
 # Compress