Spec is not inferred correctly for multi-value argument

[oakad]

Let's say I have a command with a multi-value argument of the following sort:

cmdArgs.StringsArgPtr(
	&cmd.args.srcs,
	"SOURCE_PATHS",
	nil,
	"Directories or files to load",
)

The automatically inferred spec for it will (incorrectly) be "something something SOURCE_PATHS". This will incorrectly reject multiple "source path" arguments with an "incorrect usage" error (only a single argument will be allowed).

The correct, working spec can be specified explicitly to fix the issue: "something something SOURCE_PATHS...".

However, it seems that multi-value argument constructor can be made a little smarter to add ellipsis to spec automatically.