make pubkey print out key in ssh encoding, add --pem flag for old for…

…mat, fixes #50

README.md

@@ -424,11 +424,17 @@ Outputs the public key for a repository.
     $ travis pubkey
     Public key for travis-ci/travis:
 
+    ssh-rsa ...
+    $ travis pubkey -r rails/rails > rails.key
+
+The `--pem` flag will print out the key PEM encoded:
+
+    $ travis pubkey --pem
+    Public key for travis-ci/travis:
+
     -----BEGIN PUBLIC KEY-----
     ...
     -----END PUBLIC KEY-----
-
-    $ travis pubkey -r rails/rails > rails.key
 
 #### `restart`
 

lib/travis/cli/pubkey.rb

@@ -4,14 +4,17 @@
 module Travis
   module CLI
     class Pubkey < RepoCommand
+      on('-p', '--[no-]pem', 'encode in format used by pem')
+
       def run
         say key, "Public key for #{color(repository.slug, :info)}:\n\n%s", :bold
       end
 
       private
 
         def key
-          repository.public_key.to_s
+          key = repository.public_key
+          pem? ? key.to_s : key.to_ssh
         end
     end
   end

lib/travis/client/repository.rb

@@ -17,6 +17,10 @@ def encrypt(value)
           Base64.encode64(encrypted).gsub(/\s+/, "")
         end
 
+        def to_ssh
+          ['ssh-rsa ', "\0\0\0\assh-rsa#{sized_bytes(to_rsa.e)}#{sized_bytes(to_rsa.n)}"].pack('a*m').gsub("\n", '')
+        end
+
         def to_rsa
           @to_rsa ||= OpenSSL::PKey::RSA.new(to_s)
         rescue OpenSSL::PKey::RSAError
@@ -27,6 +31,18 @@ def to_rsa
         def ==(other)
           other.to_s == self
         end
+
+        private
+
+          def sized_bytes(value)
+            bytes = to_byte_array(value.to_i)
+            [bytes.size, *bytes].pack('NC*')
+          end
+
+          def to_byte_array(num, *significant)
+            return significant if num.between?(-1, 0) and significant[0][7] == num[7]
+            to_byte_array(*num.divmod(256)) + significant
+          end
       end
 
       include States