- similar to the behaviour of std::ignore and consistent with the
  no input / no output nature of nullObject. Similarly accept a
  const reference for its Istream operator.

- make most nullObject methods constexpr

- mostly wraps std::chrono so can inline much of it, which is potentially
  helpful when used for inner timings.

- add elapsedTime() method for direct cast to double and for
  naming similarity with wall-clock method.

Potential breaking change (minor):

- clockValue construct with a bool parameter is now simply tagged
  dispatch (value is ignored) and always queries the current clock
  value. This avoids needless branching.
  Since this constructor form has primarily been used internally (eg,
  clockTime), breakages in user code are not expected.

- makes format of ExecutionTime = ... output configurable (#788)
  and reduces code clutter.

- have printBuildInfo output to std::ostream
- removed extraneous include "stdFoam.H"

ENH: revert to pre-processor defines for hard-coded paths (#1712)

- redundant information, but more robust at run-time without relying
  on initialization order

- add clang test, don't complaint about dash, zsh

- don't bother with checking gzip and tar

- previously could only run from the project directory

- strip surrounding double quotes on input of path names
  since they are added automatically when editing.

- interDyMFoam, multiphaseInterDyMFoam, pimpleDyMFoam, rhoPimpleDyMFoam
- surfaceMeshTriangulate

COMP: do not rely on implicit conversion to PtrList from Istream

- can define spatial/temporal variations for heat-flux or
  convection coefficient.

- can define temporal variations for power or ambient temperature

- exhibited apparent issues with initialization order (on some
  installations of gcc-4.8.5) when a variable was used.

ENH: eliminate duplicate input region types

- previously relied on presence/absence of command-line options.
  Can now explicitly disable individually

- provide shorter constructors for dealing with these types of cases.
  Make construction with non-default names for "system" and "constant"
  lengthier so there is no ambiguity.

- lookup a fvPatch given a polyPatch reference.
  Replaces ad hoc helpers in patchExprFieldBase

- this does mean two passes are required on the initial compilation,
  but improves reliability thereafter.

ENH: correct csh handling of system paraview

- now treating as an optional component

OpenFOAM bot authored May 22, 2020 and Mark OLESEN committed May 22, 2020

COMP: deletion of incomplete type

multiphaseReactingTurbulenceModels and twoPhaseReactingTurbulenceModels
add models to the same table TurbulenceModel. These two libs were removed
from libreactingPhaseSystem which created the conflict.

The multiphaseReactingTurbulenceModels was added to
reactingMultiPhaseEulerFoam solver and twoPhaseReactingTurbulenceModels to
twoPhaseReactingEulerFoam solver

The FO heatTransferCoeffs for libfieldFunctionObjects needs
twoPhaseReactingTurbulenceModels.

These change avoids linking conflict from multiphaseReactingTurbulenceModels
and twoPhaseReactingTurbulenceModels being linked in the same lib.

support eulersolver heat transfer fo

See merge request !333

Explicitly avoid updating cyclicACMI.

Feature build granularity

See merge request !359

Mark OLESEN authored May 11, 2020 and Andrew Heather committed May 19, 2020

- Provide Allwmake-mpi scripts for handling the MPI-only build segment.

- Adjust Make/options to support a FOAM_MPI_LIBBIN target location.
  This will simply default to FOAM_LIBBIN/FOAM_MPI, but allows different
  types of builds with out-of-tree targets.

Example,

Build OpenFOAM with default MPI settings (eg, system openmpi)
```
./Allwmake
```

Rebuild MPI-layers with different MPI.

For any given and known type
```
othermpi()
{
    export WM_MPLIB=OPENMPI
    export FOAM_MPI=openmpi-3.1.3

    export OPAL_PREFIX=$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER/$FOAM_MPI
    export MPI_ARCH_PATH="$OPAL_PREFIX"
}
```

May wish to build/rebuild ptscotch
```
(
    othermpi
    $WM_THIRD_PARTY_DIR/makeSCOTCH
)
```

Rebuild the mpi-dependent parts. Can also provide install location
```
for script in $(find src -name Allwmake-mpi)
do
(
    other_mpi
    export FOAM_MPI_LIBBIN="$HOME/tmp/install-prefix/lib/$FOAM_MPI"
)
done
```

Mark OLESEN authored May 15, 2020 and Andrew Heather committed May 19, 2020

- improve wmake CGAL rule(s) accordingly

Mark OLESEN authored May 15, 2020 and Andrew Heather committed May 19, 2020

- adds some more flexibility

For example,

    const edge meshE(patch.meshPoints(), patch.edges()[edgei]);

- purpose is to preserve empty directories under git, so use the more
  general name

The final leak can only be decided once all cells have been
deleted. So only exit on final invocation and give warning-only
beforehand. This avoids a lot of false positives.
The tutorial itself didn't actually produce a mesh with leakage
with the old settings. Upped the refinement level to force it
to go through the hole in the geometry.

This makes coded versions easier.