t/*: rearrange tests into numbered directories.

It was getting way too ad-hoc in there.  Let's reorganize the tests so that
there's a good, obvious, suggested sequence to run them in.

t/250-makedir/dirtest/all.do

@@ -0,0 +1,16 @@
+rm -f log dir1/log dir1/stinky
+touch t1.do
+../../flush-cache
+redo t1
+touch t1.do
+../../flush-cache
+redo t1
+../../flush-cache
+redo-ifchange t1
+C1="$(wc -l <dir1/log)"
+C2="$(wc -l <log)"
+. ../../skip-if-minimal-do.sh
+if [ "$C1" -ne 1 -o "$C2" -ne 2 ]; then
+	echo "failed: t1>t1, c1=$C1, c2=$C2" >&2
+	exit 55
+fi