degen: consider common outgoing acceptance only inside an SCC

* src/tgbaalgos/degen.cc: Here.
* src/tgbatest/degenid.test: Add a test case that is improved
by this.
* src/tgbatest/ltl2ta.test, src/tgbatest/ltl2tgba.test: Adjust.

src/tgbatest/degenid.test

@@ -103,3 +103,91 @@ grep 'states: 8' out
 # easy to obtain a 4-state BA when tweaking the degeneralization
 # to ignore arc entering an SCC.
 test 3 = "`../../bin/ltl2tgba -B 'G(a|G(b|Fc))' --stats=%s`"
+
+
+# This 7-state DRA (built with
+#   ltlfilt -f 'F(a & GFb) | (Fc & Fa & F(c & GF!b))' -l  |
+#   ltl2dstar --ltl2nba=spin:ltl2tgba@-sD - -
+# should be converted in into a 6-state DBA.
+cat >in.dra <<EOF
+DRA v2 explicit
+Comment: "Union{Safra[NBA=3],Safra[NBA=5]}"
+States: 7
+Acceptance-Pairs: 2
+Start: 5
+AP: 3 "a" "b" "c"
+---
+State: 0
+Acc-Sig: +0 +1
+1
+1
+2
+2
+1
+1
+2
+2
+State: 1
+Acc-Sig: +1
+1
+1
+2
+2
+1
+1
+2
+2
+State: 2
+Acc-Sig: +0
+1
+1
+2
+2
+1
+1
+2
+2
+State: 3
+Acc-Sig: +0
+6
+6
+3
+3
+1
+1
+0
+0
+State: 4
+Acc-Sig:
+4
+0
+4
+0
+4
+0
+4
+0
+State: 5
+Acc-Sig:
+5
+3
+5
+3
+4
+0
+4
+0
+State: 6
+Acc-Sig:
+6
+6
+3
+3
+1
+1
+0
+0
+EOF
+
+run 0 ../../bin/dstar2tgba in.dra -BD --stats=%s > out.stat
+test 6 = "`cat out.stat`"