set explicit tags for SIRF-Exercises and SIRF-contribs

[KrisThielemans]

We currently default to origin/master but that will break things at some point. This would be important for PETRIC as well (need to have a reproducible set-up)

[KrisThielemans]

SIRF-contribs

SIRF-SuperBuild/version_config.cmake

Line 152 in d6b449a

set(DEFAULT_SIRF-Contribs_TAG origin/master)

so let's add this to our Release task list.

SIRF-Exercises

This is far more complicated, see lines below. Doing this properly awaits a SIRF pypy project, so at present we will only tag SIRF-Exercsies, but not use the tag in the install scripts yet.

SIRF-SuperBuild/VirtualBox/scripts/UPDATE.sh

Lines 131 to 137 in d6b449a

	cd $SIRF_SRC_PATH
	clone_or_pull https://github.com/SyneRBI/SIRF-Exercises.git
	cd $SIRF_SRC_PATH/SIRF-Exercises
	# Python (runtime)
	if [ -f requirements.txt ]; then
	"$PYTHON_EXECUTABLE" -m pip install -U -r requirements.txt
	fi

SIRF-SuperBuild/docker/user_demos.sh

Lines 12 to 54 in d6b449a

	git clone https://github.com/SyneRBI/SIRF-Exercises --recursive $INSTALL_DIR/SIRF-Exercises
	#install SIRF-Exercises requirements
	cd $INSTALL_DIR/SIRF-Exercises
	if [ "$PYTHON" = "miniconda" ]; then
	if [ -f environment.yml ]; then
	if test "${BUILD_GPU:-0}" != 0; then
	# uncomment GPU deps
	sed -r 's/^(\s*)#\s*(- \S+.*#.*GPU.*)$/\1\2/' environment.yml > environment-sirf.yml
	else
	# delete GPU deps
	sed -r -e '/^\s*- (astra-toolbox|tigre).*/d' -e '/^\s*- \S+.*#.*GPU/d' environment.yml > environment-sirf.yml
	fi
	# do not install CIL from conda if BUILD_CIL is set
	if test "${BUILD_CIL:-OFF}" != "OFF"; then
	# delete CIL package from the environment file
	echo "Deleting CIL from the environment file BUILD_CIL is set to >${BUILD_CIL}<"
	sed -r -i -e '/^\s*- (cil).*/d' environment-sirf.yml
	cat environment-sirf.yml
	else
	echo "Not deleting CIL from the environment file BUILD_CIL is set to >${BUILD_CIL}<"
	fi
	conda env update --file environment-sirf.yml
	else
	if [ -f requirements.txt ]; then
	cat requirements.txt
	# installing the requirements.txt with conda requires some cleaning of the requirements.txt
	# Also the requirements.txt contains some packages that are not found on conda-forge, i.e. brainweb
	# Therefore, these need to be installed by pip.
	# This is handled by the install-sirf-exercises-dep.py script
	python ~/install-sirf-exercises-dep.py requirements.txt
	else
	echo "SIRF-Exercises requirements: did not find requirements.txt nor environment.yml. Skipping"
	fi
	fi
	else
	if [ -f requirements.txt ]; then
	# just install the requirements.txt with pip
	${PYTHON} -m pip install -U -r requirements.txt
	else
	echo "SIRF-Exercises requirements: did not find requirements.txt. Skipping"
	fi
	fi