optimize BDDSourceManager

[anothermattbrown]

When no sources are referenced, we don't need a representative of the
active but unreferenced sources. Not having one makes the manager
trivial, which makes source tracking more efficient.

[batfish-bot]

This change is 

[dhalperi]

Reviewed 2 of 2 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @anothermattbrown)

---

projects/batfish-common-protocol/src/test/java/org/batfish/common/bdd/BDDSourceManagerTest.java, line 204 at r1 (raw file):

    Map<String, Configuration> configs = ImmutableMap.of(hostname, config);
    BDDSourceManager mgr = BDDSourceManager.forNetwork(_pkt, configs, true).get(hostname);
    assertTrue(mgr.isTrivial());

no tests where we assert the opposite?

[anothermattbrown]

Reviewable status: 1 of 2 files reviewed, 1 unresolved discussion (waiting on @dhalperi)

---

projects/batfish-common-protocol/src/test/java/org/batfish/common/bdd/BDDSourceManagerTest.java, line 204 at r1 (raw file):

Previously, dhalperi (Dan Halperin) wrote…

no tests where we assert the opposite?

added some

[dhalperi]

Reviewed 1 of 1 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved

[codecov]

Codecov Report

Merging #3935 into master will decrease coverage by <.01%.
The diff coverage is 92.3%.

@@             Coverage Diff              @@
##             master    #3935      +/-   ##
============================================
- Coverage     74.86%   74.86%   -0.01%     
- Complexity    24089    24092       +3     
============================================
  Files          2027     2027              
  Lines         96668    96672       +4     
  Branches      11509    11512       +3     
============================================
+ Hits          72367    72369       +2     
- Misses        19044    19050       +6     
+ Partials       5257     5253       -4

Impacted Files	Coverage Δ	Complexity Δ
.../java/org/batfish/common/bdd/BDDSourceManager.java	96.33% <92.3%> (+1.04%)	48 <9> (+6)	⬆️
.../src/main/java/org/batfish/datamodel/flow/Hop.java	53.33% <0%> (-6.67%)	5% <0%> (-1%)
...org/batfish/datamodel/flow/BidirectionalTrace.java	79.54% <0%> (-4.55%)	13% <0%> (-2%)
...rc/main/java/org/batfish/datamodel/flow/Trace.java	87.09% <0%> (-3.23%)	11% <0%> (-2%)
...ava/org/batfish/datamodel/bgp/Layer2VniConfig.java	85.71% <0%> (-2.86%)	15% <0%> (-1%)
...col/src/main/java/org/batfish/role/InferRoles.java	91.24% <0%> (-0.37%)	68% <0%> (-1%)
...tfish/representation/cisco/CiscoConfiguration.java	83.8% <0%> (-0.13%)	530% <0%> (-1%)
...presentation/cumulus/CumulusNcluConfiguration.java	94.5% <0%> (+0.01%)	128% <0%> (ø)	⬇️
...src/main/java/org/batfish/coordinator/PoolMgr.java	65.16% <0%> (+1.12%)	16% <0%> (+1%)	⬆️
...ain/java/org/batfish/symbolic/IngressLocation.java	68.42% <0%> (+2.63%)	16% <0%> (+1%)	⬆️
... and 2 more

[dhalperi]

Reviewed 1 of 1 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved

[dhalperi]

Reviewed 1 of 1 files at r4.
Reviewable status: complete! all files reviewed, all discussions resolved