cli: Add simple mode --disk size=X

Works the same as pool=default, we generate a disk image path and
create it in the default pool.

man/virt-install.pod

@@ -473,9 +473,13 @@ general format of a disk string is
 
     --disk opt1=val1,opt2=val2,...
 
-To specify media, the command can either be:
+The simplest invocation to create a new 10G disk image and associated disk device:
 
-    --disk /some/storage/path,opt1=val1
+    --disk size=10
+
+virt-install will generate a path name, and place it in the default image location for the hypervisor. To specify media, the command can either be:
+
+    --disk /some/storage/path[,opt1=val1]...
 
 or explicitly specify one of the following arguments:
 
@@ -1422,7 +1426,7 @@ CDROM drive, auto launching a graphical VNC viewer
        --virt-type kvm \
        --name demo \
        --memory 500 \
-       --disk path=/var/lib/libvirt/images/demo.img,size=8 \
+       --disk size=8 \
        --graphics vnc \
        --cdrom /dev/cdrom \
        --os-variant fedora13

tests/clitest.py

@@ -653,6 +653,7 @@ c = vinst.add_category("remote", "--connect %(REMOTEURI)s --nographics --noautoc
 c.add_valid("--nodisks --pxe")  # Simple pxe nodisks
 c.add_valid("--pxe --disk vol=%(POOL)s/%(VOL)s")  # Using existing managed storage 2
 c.add_valid("--pxe --disk pool=%(POOL)s,size=.04")  # Creating storage on managed pool
+c.add_valid("--pxe --disk size=.04")  # Creating storage on implied pool=default
 c.add_valid("--pxe --disk /foo/bar/baz,size=.01")  # Creating any random path on the remote host
 c.add_valid("--pxe --disk /dev/zde")  # /dev file that we just pass through to the remote VM
 c.add_invalid("--pxe --disk /foo/bar/baz")  # File that doesn't exist after auto storage setup
@@ -707,7 +708,6 @@ c.add_invalid("--file %(NEWIMG1)s --file-size 100000 --nonsparse")  # Nonexistin
 c.add_invalid("--file %(NEWIMG1)s --file-size 100000")  # Huge file, sparse, but no prompting
 c.add_invalid("--file %(NEWIMG1)s")  # Nonexisting file, no size
 c.add_invalid("--file %(EXISTIMG1)s --file %(EXISTIMG1)s --file %(EXISTIMG1)s --file %(EXISTIMG1)s --file %(EXISTIMG1)s")  # Too many IDE
-c.add_invalid("--file-size .0001")  # Size, no file
 c.add_invalid("--disk pool=foopool,size=.0001")  # Specify a nonexistent pool
 c.add_invalid("--disk vol=%(POOL)s/foovol")  # Specify a nonexistent volume
 c.add_invalid("--disk pool=%(POOL)s")  # Specify a pool with no size

virtinst/cli.py

@@ -806,8 +806,8 @@ def add_disk_option(stog, editexample=False):
         editmsg += "\n--disk cache=  (unset cache)"
     stog.add_argument("--disk", action="append",
         help=_("Specify storage with various options. Ex.\n"
-               "--disk path=/my/existing/disk\n"
-               "--disk path=/my/new/disk,size=5 (in gigabytes)\n"
+               "--disk size=10 (new 10GB image in default location)\n"
+               "--disk path=/my/existing/disk,cache=none\n"
                "--disk device=cdrom,bus=scsi\n"
                "--disk=?") + editmsg)
 
@@ -1528,8 +1528,12 @@ def _parse_disk_source(guest, path, pool, vol, size, fmt, sparse):
     volobj = None
 
     # Strip media type
-    if sum([bool(p) for p in [path, pool, vol]]) > 1:
+    optcount = sum([bool(p) for p in [path, pool, vol]])
+    if optcount > 1:
         fail(_("Cannot specify more than 1 storage path"))
+    if optcount == 0 and size:
+        # Saw something like --disk size=X, have it imply pool=default
+        pool = "default"
 
     if path:
         abspath = os.path.abspath(path)