⚡ Better handling of a local, not-specified-at-runtime Singularity image

[shnizzedy]

Related problem

Right now, if --platform singularity is given without an image, cpac just pulls without even trying to find a local image.

cpac/src/cpac/backends/singularity.py

Lines 29 to 40 in a05d612

	else: # pragma: no cover
	try:
	self.image = Client.pull(
	"shub://FCP-INDI/C-PAC",
	pull_folder=pwd
	)
	except Exception:
	try:
	self.image = Client.pull(
	f"docker://fcpindi/c-pac:latest",
	pull_folder=pwd
	)

Proposed feature

A configuration file that specifies the path to a default Singularity image seems like the most obvious solution.

Alternatives

• A default path?
• An environment variable?