Allow "-d" and "-r" coexisting in sf project retrieve start

[xixiaofinland]

I have the desire to pull a metadata file from a given org and diff it with my existing local copy. I assume "sf project retrieve start" is the command to use.

As I already have the metadata file locally, I wish to use "-d" (full path) to specify precisely which file to pull from the org.
I also wish to use "-r" to give a temp local location to save the pulled copy.

However, the issue is: "-d" and "-r" cannot coexist, sf command returns error.

Alternatively, I can use "-m" and "-r" combination, but "-m" needs to tell which metadata type the file is, this is suboptimal.