Correctly handle a checksummed file that depends on a non-checksummed file.

We were rebuilding the checksummed file every time because redo-ifchange was
incorrectly assuming that a child's changed_runid that's greater than my
changed_runid means I'm dirty.  But if my checked_runid is >= the child's
checked_runid, then I'm clean, because my checksum didn't change.

Clear as mud?

t/flush-cache.sh

@@ -3,7 +3,7 @@
 (
 	echo ".timeout 5000"
 	echo "pragma synchronous = off;"
-	echo "update Files set checked_runid=null, " \
+	echo "update Files set checked_runid=checked_runid-1, " \
 	     "       changed_runid=changed_runid-1, " \
 	     "       failed_runid=failed_runid-1;"
 ) | sqlite3  "$REDO_BASE/.redo/db.sqlite3"

t/stamp/.gitignore

@@ -2,3 +2,4 @@
 /usestamp
 /stampy
 /inp
+/bob

t/stamp/bob.do

@@ -0,0 +1 @@
+echo $$

t/stamp/clean.do

@@ -1 +1 @@
-rm -f *.log usestamp stampy inp *~ .*~
+rm -f *.log usestamp stampy inp bob *~ .*~

t/stamp/stamptest.do

@@ -18,12 +18,23 @@ redo-ifchange usestamp
 [ "$(wc -l <stampy.log)" -eq 2 ] || exit 41
 [ "$(wc -l <usestamp.log)" -eq 1 ] || exit 42
 
+../flush-cache.sh
+redo bob
+redo-ifchange usestamp
+[ "$(wc -l <stampy.log)" -eq 3 ] || exit 43
+[ "$(wc -l <usestamp.log)" -eq 2 ] || exit 44
+
+../flush-cache.sh
+redo-ifchange usestamp
+[ "$(wc -l <stampy.log)" -eq 3 ] || exit 45
+[ "$(wc -l <usestamp.log)" -eq 2 ] || exit 46
+
 ../flush-cache.sh
 echo two >inp
 redo stampy
-[ "$(wc -l <stampy.log)" -eq 3 ] || exit 51
-[ "$(wc -l <usestamp.log)" -eq 1 ] || exit 52
+[ "$(wc -l <stampy.log)" -eq 4 ] || exit 51
+[ "$(wc -l <usestamp.log)" -eq 2 ] || exit 52
 
 redo-ifchange usestamp
-[ "$(wc -l <stampy.log)" -eq 3 ] || exit 61
-[ "$(wc -l <usestamp.log)" -eq 2 ] || exit 62
+[ "$(wc -l <stampy.log)" -eq 4 ] || exit 61
+[ "$(wc -l <usestamp.log)" -eq 3 ] || exit 62

t/stamp/stampy.do

@@ -1,3 +1,4 @@
 echo $$ >>stampy.log
+redo-ifchange inp bob
 cat inp
 redo-stamp <inp