sysupdate: insert tombstone

after this update, we're on git: update sysupdate
to switch repositories.

rc/bin/sysupdate

@@ -1,17 +1,35 @@
 #!/bin/rc
+
 rfork en
-source=https://code.9front.org/hg/plan9front
-cd /
-if(! test -d .hg)
-	bind -ac /dist/plan9front /
-while(! ~ $#* 0){
-	switch($1){
-	case -i
-		hg incoming $source
-	case *
-		echo usage: sysupdate '[-i]' >[1=2]
-		exit usage
+
+updating=()
+nl='
+'
+if(! test -d /dist/plan9front/.git){
+	>[1=2] echo 'end of line for hg: moving to git.'
+	updating=1
+
+	if(! test -f /bin/git/pull){
+		>[1=2] echo 'git is required:'
+		>[1=2] echo '	cd /sys/src/cmd/git && mk install'
+		exit gitless
 	}
-	shift
+
+	>[1=2] echo '	fetching snapshot...'
+	cd /dist/plan9front
+	hget http://git.9front.org/static/plan9front-seed.tar.gz | tar xz
+	mv .git-snap .git
+
+	git/fs
+	git/walk >/dev/null
+	>[1=2] echo '	pulling with git...'
 }
-hg -v pull -u $source
+
+cd /
+if(! test -d .git)
+	bind -ac /dist/plan9front /
+git/pull -u gits://git.9front.org/plan9front/plan9front
+
+if(~ $updating 1)
+	>[1=2] echo 'got git: you may remove /dist/plan9front/.hg'
+exit ''