{ood,sources,targets}: fix relative paths; turn missing targets into sources.

When we check dependencies and a previously-is_generated dependency
existed before, but no longer does, forget that it was is_generated.
This slightly improves the situation where as a project evolves, a file
that used to be a target gets removed, and then later is re-added as a
static source file.  (It doesn't fix the other variant, where a file is
changed from target to source in a single atomic change, and is never
missing.  That one will be trickier to handle.)

While adding a test for this behaviour, I discovered that redo-sources,
redo-targets, and redo-ood were reporting their output relative to
STARTDIR instead of relative to $PWD, so fix that too.

t/102-empty/clean.do

@@ -1 +1 @@
-rm -f touch1 touch1-ran *~ .*~
+rm -f touch1 touch1-ran *~ .*~ silence.do

t/351-deps-forget/.gitignore

@@ -0,0 +1,6 @@
+bork
+bork.do
+bork.log
+sub
+sub.log
+targets.out

t/351-deps-forget/all.do

@@ -0,0 +1,55 @@
+exec >&2
+rm -f bork.do bork bork.log sub sub.log targets.out
+
+qgrep() {
+	# like "grep -q", but portable
+	grep "$@" >/dev/null
+}
+
+cp bork.do.in bork.do
+redo bork
+[ "$(cat bork.log)" = "x" ] || exit 2
+redo bork
+[ "$(cat bork.log)" = "xx" ] || exit 3
+
+redo-ifchange sub
+[ "$(cat bork.log)" = "xx" ] || exit 10
+[ "$(cat sub.log)" = "y" ] || exit 11
+. ../skip-if-minimal-do.sh
+redo-sources | qgrep '^bork$' && exit 12
+redo-targets | tee targets.out | qgrep '^bork$' || exit 13
+
+# Might as well test redo-ood while we're here
+../flush-cache
+redo bork
+redo-targets | qgrep '^bork$' || exit 15
+redo-targets | qgrep '^sub$'  || exit 16
+redo-ood     | qgrep '^sub$'  || exit 17
+
+redo-ifchange sub
+[ "$(cat bork.log)" = "xxx" ] || exit 18
+[ "$(cat sub.log)" = "yy" ] || exit 19
+
+rm -f bork
+../flush-cache
+redo-ifchange sub  # rebuilds, and sub.do drops dependency on bork
+[ "$(cat bork.log)" = "xxx" ] || exit 20
+[ "$(cat sub.log)" = "yyy" ] || exit 21
+redo-sources | qgrep '^bork$' && exit 22  # nonexistent, so not a source
+redo-targets | qgrep '^bork$' && exit 23  # deleted; not a target anymore
+
+echo static >bork
+../flush-cache
+redo-ifchange sub  # doesn't depend on bork anymore, so doesn't rebuild
+[ "$(cat bork.log)" = "xxx" ] || exit 30
+[ "$(cat sub.log)" = "yyy" ] || exit 31
+
+# bork should now be considered static, so no warning or need to rebuild.
+# It should now be considered a source, not a target.
+redo sub  # force rebuild; sub.do now declares dependency on bork
+[ "$(cat bork.log)" = "xxx" ] || exit 40
+[ "$(cat sub.log)" = "yyyy" ] || exit 41
+redo-sources | qgrep '^bork$' || exit 42
+redo-targets | qgrep '^bork$' && exit 43
+
+exit 0

t/351-deps-forget/bork.do.in

@@ -0,0 +1,2 @@
+echo bork
+printf x >>$1.log

t/351-deps-forget/clean.do

@@ -0,0 +1,2 @@
+rm -f *~ .*~ bork bork.do bork.log sub sub.log targets.out
+

t/351-deps-forget/sub.do

@@ -0,0 +1,3 @@
+[ -e bork ] && redo-ifchange bork
+echo sub
+printf y >>$1.log