Allow firmware update by version or latest from releases.json

trezorctl

@@ -203,9 +203,6 @@ class Commands(object):
         return ret
 
     def firmware_update(self, args):
-        if not args.file and not args.url:
-            raise Exception("Must provide firmware filename or URL")
-
         if args.file:
             fp = open(args.file, 'r')
         elif args.url:
@@ -213,6 +210,19 @@ class Commands(object):
             resp = urllib.urlretrieve(args.url)
             fp = open(resp[0], 'r')
             urllib.urlcleanup() # We still keep file pointer open
+        else:
+            resp = urllib.urlopen("https://mytrezor.com/data/firmware/releases.json")
+            releases = json.load(resp)
+            version = lambda r: r['version']
+            version_string = lambda r: ".".join(map(str, version(r)))
+            if args.version:
+                release = next((r for r in releases if version_string(r) == args.version))
+            else:
+                release = max(releases, key=version)
+                print "No file, url, or version given. Fetching latest version: %s" % version_string(release)
+            print "Firmware fingerprint: %s" % release['fingerprint']
+            args.url = release['url']
+            return self.firmware_update(args)
 
         if fp.read(8) == '54525a52':
             print "Converting firmware to binary"
@@ -358,6 +368,7 @@ class Commands(object):
     firmware_update.arguments = (
         (('-f', '--file'), {'type': str}),
         (('-u', '--url'), {'type': str}),
+        (('-n', '--version'), {'type': str}),
     )
 
 def list_usb():