reference: introduce remoteName variable

This pattern was used in two places, so adding an intermediate variable allows
documenting its purpose. The "remote-name" grammer (which is interchangably
used with "path") also seemed to be missing from the grammar, so adding it.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

reference/reference.go

@@ -4,13 +4,14 @@
 // Grammar
 //
 //	reference                       := name [ ":" tag ] [ "@" digest ]
-//	name                            := [domain '/'] path-component ['/' path-component]*
+//	name                            := [domain '/'] remote-name
 //	domain                          := host [':' port-number]
 //	host                            := domain-name | IPv4address | \[ IPv6address \]	; rfc3986 appendix-A
 //	domain-name                     := domain-component ['.' domain-component]*
 //	domain-component                := /([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])/
 //	port-number                     := /[0-9]+/
 //	path-component                  := alpha-numeric [separator alpha-numeric]*
+//	path (or "remote-name")         := path-component ['/' path-component]*
 //	alpha-numeric                   := /[a-z0-9]+/
 //	separator                       := /[_.]|__|[-]*/
 //