Dataflow: Restrict partial flow to either forward or reverse flow.

[aschackmull]

When using partial flow we would calculate both partial forward flow and partial reverse flow even though only one direction was requested. This moves the choice into the parameterised module application so we know up front which one to calculate. So instead of always using module Partial = FlowExploration<limit/0> and choosing between Partial::partialFlow and Partial::partialFlowRev, you now choose between module Partial = FlowExplorationFwd<limit/0> and module Partial = FlowExplorationRev<limit/0>, and then always use Partial::partialFlow.

[MathiasVP]

LGTM! I guess we should also update the reference to FlowExploration in https://codeql.github.com/docs/writing-codeql-queries/debugging-data-flow-queries-using-partial-flow/ (or make FlowExploration an alias for FlowExplorationFwd)?

[aschackmull]

I guess we should also update the reference to FlowExploration

The doc needs an update regardless as the info about reverse flow needs a fix.

[MathiasVP]

The code changes LGTM! Should we have the Docs team 👀 the documentation changes?

[aschackmull]

Should we have the Docs team 👀 the documentation changes?

It's very minor, so I think your review is plenty.

[alexet]

Do you need to update the test queries in java/ql/test/library-tests/dataflow/partial?

[aschackmull]

Do you need to update the test queries in java/ql/test/library-tests/dataflow/partial?

Gah! Of course CI didn't run.