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/660-stamp/stamptest.do

@@ -0,0 +1,72 @@
+rm -f stampy usestamp usestamp2 stampy.log usestamp.log usestamp2.log
+echo one >inp
+
+../flush-cache
+redo stampy
+[ "$(wc -l <stampy.log)" -eq 1 ] || exit 11
+
+# stampy already exists, so we won't generate it a second time, even though
+# usestamp depends on it.
+../flush-cache
+redo-ifchange usestamp
+[ "$(wc -l <stampy.log)" -eq 1 ] || exit 21
+[ "$(wc -l <usestamp.log)" -eq 1 ] || exit 12
+
+../flush-cache
+redo stampy
+. ../skip-if-minimal-do.sh
+[ "$(wc -l <stampy.log)" -eq 2 ] || exit 31
+[ "$(wc -l <usestamp.log)" -eq 1 ] || exit 32
+
+# same as above: stampy is already up-to-date, so it won't be redone.
+../flush-cache
+redo-ifchange usestamp
+[ "$(wc -l <stampy.log)" -eq 2 ] || exit 41
+[ "$(wc -l <usestamp.log)" -eq 1 ] || exit 42
+
+# stampy depends on bob, so we'll have to rebuild stampy automatically.  But
+# stampy's checksum will still be identical, so usestamp shouldn't rebuild.
+../flush-cache
+redo bob
+../flush-cache
+redo-ifchange usestamp
+[ "$(wc -l <stampy.log)" -eq 3 ] || exit 43
+[ "$(wc -l <usestamp.log)" -eq 1 ] || exit 44
+
+# Make sure the previous step correctly marked stampy and usestamp as
+# up-to-date even though *neither* of them is newer than bob.
+../flush-cache
+redo-ifchange usestamp
+[ "$(wc -l <stampy.log)" -eq 3 ] || exit 45
+[ "$(wc -l <usestamp.log)" -eq 1 ] || exit 46
+
+# now we're changing the contents of stampy.  Thus usestamp will need to
+# be rebuilt, but not yet...
+echo two >inp
+../flush-cache
+redo stampy
+[ "$(wc -l <stampy.log)" -eq 4 ] || exit 51
+[ "$(wc -l <usestamp.log)" -eq 1 ] || exit 52
+
+# let's see about usestamp.  It needs to be rebuilt because stampy has changed,
+# but since stampy is *already* changed, stampy itself shouldn't be re-rebuilt.
+../flush-cache
+redo-ifchange usestamp usestamp2
+[ "$(wc -l <stampy.log)" -eq 4 ] || exit 61
+[ "$(wc -l <usestamp.log)" -eq 2 ] || exit 62
+[ "$(wc -l <usestamp2.log)" -eq 1 ] || exit 62
+
+# when we delete the file and it gets regenerated identically, it's as good as
+# never having been deleted.  So usestamp won't need to change.
+../flush-cache
+rm -f stampy
+redo-ifchange usestamp usestamp2
+[ "$(wc -l <stampy.log)" -eq 5 ] || exit 71
+[ "$(wc -l <usestamp.log)" -eq 2 ] || exit 72
+[ "$(wc -l <usestamp2.log)" -eq 1 ] || exit 73
+
+# this simple test used to cause a deadlock.
+../flush-cache
+rm -f stampy
+redo-ifchange stampy
+[ "$(wc -l <stampy.log)" -eq 6 ] || exit 74