SUBMODULE: relocate community repos into plugins/ directory

- new landing place for general community repositories

.gitmodules

@@ -1,8 +1,8 @@
 [submodule "cfmesh"]
-	path = modules/cfmesh
+	path = plugins/cfmesh
 	url = https://develop.openfoam.com/Community/integration-cfmesh.git
 [submodule "avalanche"]
-	path = modules/avalanche
+	path = plugins/avalanche
 	url = https://develop.openfoam.com/Community/avalanche.git
 [submodule "adios"]
 	path = modules/adios
@@ -18,5 +18,5 @@
 	path = modules/external-solver
 	url = https://develop.openfoam.com/Modules/external-solver.git
 [submodule "turbulence-community"]
-	path = modules/turbulence-community
+	path = plugins/turbulence-community
 	url = https://gitlab.com/openfoam/community/tc-turbulence/turbulence-community.git

plugins/Allwmake

@@ -0,0 +1,42 @@
+#!/bin/sh
+cd "${0%/*}" || exit                            # Run from this directory
+targetType=libso
+. "${WM_PROJECT_DIR:?}"/wmake/scripts/AllwmakeParseArguments
+
+#------------------------------------------------------------------------------
+# Default build into OpenFOAM project locations unless specified with
+# -prefix or FOAM_MODULE_PREFIX env varable
+
+# Long form to avoid dash 0.5.8 error (issue #1757)
+[ -n "$FOAM_MODULE_PREFIX" ] || FOAM_MODULE_PREFIX="${FOAM_LIBBIN%/*}"
+export FOAM_MODULE_PREFIX
+
+echo "========================================"
+case "$FOAM_MODULE_PREFIX" in
+(false | none)
+    echo "OpenFOAM modules disabled (prefix=${FOAM_MODULE_PREFIX})"
+    echo
+    exit 0
+esac
+
+echo "prefix = $FOAM_MODULE_PREFIX"
+echo
+echo "    ignoring possible compilation errors"
+echo "    make certain to check the output file"
+echo
+set +e
+export WM_CONTINUE_ON_ERROR=true
+
+#------------------------------------------------------------------------------
+
+for name in $(./list-plugins)
+do
+    if [ -d "$name" ]
+    then
+        # Use wmake -all instead of Allwmake to allow for overrides
+        ( cd "$name" && wmake -all $targetType )
+    fi
+done
+
+
+#------------------------------------------------------------------------------

plugins/README.md

@@ -0,0 +1,134 @@
+[[_TOC_]]
+
+## OpenFOAM Plugins
+
+This directory is a location for additional OpenFOAM components or
+tools to placed and have them built as part of the normal OpenFOAM
+build process. It is assumed that each subdirectory contain an
+appropriate `Allwmake` (or `Allwmake.override`) file.
+
+### How to use
+
+On the first use, you need to register the submodules, and then update them.
+You can execute both steps for all the available submodules (including the
+nested ones) as follows while you are at `$WM_PROJECT_DIR`:
+
+```bash
+cd $WM_PROJECT_DIR
+
+git submodule update --init --recursive
+```
+
+Executing this single-line command clones all the submodules from their
+respective repositories and prepares them for compilation. Note that you can
+also make only a certain group of submodules ready by explicitly specifying the
+requested submodules' names at the end of the command above. For example, if
+you would like to use only the `turbulence-community` submodule, you specify:
+
+```bash
+git submodule update --init --recursive plugins/turbulence-community
+```
+
+You can display information about the status of submodules as follows:
+
+```bash
+git submodule status --recursive
+```
+
+An easy way to see which submodules are actually in use:
+
+```bash
+cat .gitmodules
+```
+
+Which will reveal content resembling the following:
+```
+[submodule "xyz"]
+    path = plugins/xyz
+    url = ...
+...
+```
+
+If you need to remove a specific submodule or wish to restart the process,
+you can simply carry out the task as follows:
+
+```bash
+git submodule deinit plugins/turbulence-community
+```
+
+This command deregisters the specified submodule and clears the
+`plugins/turbulence-community` directory.
+
+A quick overview of `git submodules` can be found in this
+[*blog*][blog git-submodule] with full details in the
+[*manpage*][man git-submodule].
+
+### Build locations
+
+Any individual _plugin_ will normally also be able to exist outside of
+the plugins directory structure and will typically build into user
+locations (`$FOAM_USER_APPBIN`, `$FOAM_USER_LIBBIN`).
+
+When compiled from the top-level OpenFOAM `Allwmake` or the
+`plugins/Allwmake`, they should build into OpenFOAM project locations
+(`$FOAM_APPBIN`, `$FOAM_LIBBIN`). This can be adjusted by
+supplying an alternative `-prefix=` to the corresponding Allwmake
+command.
+
+| Command    | Install location |
+|------------|------------------|
+| ./Allwmake -prefix=user | `$FOAM_USER_APPBIN`, `$FOAM_USER_LIBBIN` |
+| ./Allwmake -prefix=group | `$FOAM_SITE_APPBIN`, `$FOAM_SITE_LIBBIN` |
+| ./Allwmake -prefix=openfoam | `$FOAM_APPBIN`, `$FOAM_LIBBIN` |
+| ./Allwmake -prefix=/some/pathname | `/some/pathname/bin`, `/some/pathname/lib` |
+
+### Documentation (doxygen)
+
+To build the doxygen information for the components, it is also
+necessary to link the directories to the doc/ subdirectory.
+This is a purely manual operation.
+
+### Developer Information
+
+#### Build locations
+
+To accomodate building into various locations, the plugin code should
+be adapted with the following changes:
+
+- ***Make/files***
+   ```
+   ...
+   EXE = $(FOAM_MODULE_APPBIN)/someExecutable
+
+   LIB = $(FOAM_MODULE_LIBBIN)/libSomeLibrary
+   ```
+
+- `Make/options` should include this
+  ```
+  include $(GENERAL_RULES)/module-path-user
+  ...
+  ```
+
+The following changes to `Make/options` are universally applicable
+(ie, work with older or other versions of OpenFOAM), but more verbose.
+
+- `Make/options` with the following
+  ```
+  sinclude $(GENERAL_RULES)/module-path-user
+
+  /* Failsafe - user locations */
+  ifeq (,$(FOAM_MODULE_APPBIN))
+  FOAM_MODULE_APPBIN = $(FOAM_USER_APPBIN)
+  endif
+  ifeq (,$(FOAM_MODULE_LIBBIN))
+  FOAM_MODULE_LIBBIN = $(FOAM_USER_LIBBIN)
+  endif
+  ...
+  ```
+
+<!-- General Information -->
+
+[man git-submodule]:  https://git-scm.com/docs/git-submodule
+[blog git-submodule]: http://blog.joncairns.com/2011/10/how-to-use-git-submodules/
+
+---

plugins/list-plugins

@@ -0,0 +1,85 @@
+#!/bin/sh
+#------------------------------------------------------------------------------
+# =========                 |
+# \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+#  \\    /   O peration     |
+#   \\  /    A nd           | www.openfoam.com
+#    \\/     M anipulation  |
+#------------------------------------------------------------------------------
+#     Copyright (C) 2020 OpenCFD Ltd.
+#------------------------------------------------------------------------------
+# SPDX-License-Identifier: (GPL-3.0-or-later)
+#
+# Script
+#     list-modules
+#
+# Description
+#     List module directories
+#     - each first-level directory with an Allwmake file
+#
+#------------------------------------------------------------------------------
+cd "${0%/*}" || exit                            # Run from this directory
+
+printHelp() {
+    cat<< HELP 1>&2
+
+Usage: ${0##*/} [OPTION]
+options:
+  -help             Display help and exit
+
+List module directories - each first-level directory with an Allwmake file
+
+HELP
+
+    exit 0  # A clean exit
+}
+
+# Report error and exit
+die()
+{
+    exec 1>&2
+    echo
+    echo "Error encountered:"
+    while [ "$#" -ge 1 ]; do echo "    $1"; shift; done
+    echo
+    echo "See '${0##*/} -help' for usage"
+    echo
+    exit 1
+}
+
+#------------------------------------------------------------------------------
+
+# Parse options
+while [ "$#" -gt 0 ]
+do
+    case "$1" in
+    -h | -help*)  # Short help
+        printHelp
+        ;;
+
+    *)
+        die "Unknown option/argument: '$1'"
+        ;;
+    esac
+    shift
+done
+
+
+# Each first-level directory with an Allwmake file
+for moduleName in *
+do
+    if [ -f "$moduleName/Allwmake" ]
+    then
+        case "$moduleName" in
+        # Skip some directory names
+        (build | doc | platform*)
+            ;;
+        (*)
+            echo "$moduleName"
+            ;;
+        esac
+    fi
+done
+
+
+#------------------------------------------------------------------------------