Add 'list-vmtargets' target, which produces a list of

all supported VM and cloud provider images.

Add VHD_DESC, VMDK_DESC, QCOW2_DESC, RAW_DESC image
descriptions.

Format the output to make a bit more readable.

Update release(7) to document the list-vmtargets target.

Sponsored by:	The FreeBSD Foundation

release/Makefile.vm

@@ -10,6 +10,11 @@ VMFORMATS?=	vhd vmdk qcow2 raw
 VMSIZE?=	20G
 VMBASE?=	vm
 
+VHD_DESC=	Azure, VirtualPC, Hyper-V, Xen disk image
+VMDK_DESC=	VMWare, VirtualBox disk image
+QCOW2_DESC=	Qemu, KVM disk image
+RAW_DESC=	Unformatted raw disk image
+
 CLOUDWARE?=	AZURE \
 		OPENSTACK
 AZURE_FORMAT=	vhdf
@@ -65,9 +70,18 @@ vm-image:
 
 vm-cloudware:	${CLOUDTARGETS}
 
+list-vmtargets:	list-cloudware
+	@${ECHO}
+	@${ECHO} "Supported virtual machine disk image formats:"
+.for FORMAT in ${VMFORMATS:tu}
+	@${ECHO} "  ${FORMAT:tl}: ${${FORMAT}_DESC}"
+.endfor
+
 list-cloudware:
 .if !empty(CLOUDWARE)
+	@${ECHO}
+	@${ECHO} "Supported cloud hosting provider images:"
 . for _CW in ${CLOUDWARE}
-	@${ECHO} "${_CW:tu}: ${${_CW:tu}_DESC}"
+	@${ECHO} "  ${_CW:tu}: ${${_CW:tu}_DESC}"
 . endfor
 .endif

share/man/man7/release.7

@@ -406,6 +406,16 @@ See
 for valid format values
 .Pq requires version 20140927 or later .
 .El
+.Pp
+For a list of supported
+.Va VMFORMATS
+values
+.Pq including cloud hosting provider formats
+along with a brief description, run:
+.Bd -literal -offset indent
+cd /usr/src
+make -C release list-vmtargets
+.Ed
 .Sh CLOUD HOSTING MACHINE IMAGES
 The
 .Fx
@@ -522,6 +532,12 @@ for implementation details.
 Displays the list of valid
 .Va CLOUDWARE
 values.
+.It Cm list-vmtargets
+Displays the list of valid
+.Va VMFORMAT
+and
+.Va CLOUDWARE
+values.
 .El
 .Pp
 Major subtargets called by targets above: