command map prefix should still use map command

it is valid use case to set both command map and prefix
in case of using different binary, the map should still be active
and prefix should be applied as extra

so following example correclty executes rake2.2 within bundler:

  SSHKit.config.command_map[:rake] = 'rake2.2'
  SSHKit.config.command_map.prefix[:rake] = 'bundle exec'

Only drawback is, that resulting command will be:

  bundle exec /usr/bin/env rake2.2

CHANGELOG.md

@@ -18,6 +18,9 @@ appear at the top.
     @beatrichartz
   * `SSHKit::Backend::Printer#test` now always returns true
     [PR #312](https://github.com/capistrano/sshkit/pull/312) @mikz
+  * when using `SSHKit::CommandMap#prefix`, resolve the command through `SSHKit::CommandMap#[]`
+    [PR #311]((https://github.com/capistrano/sshkit/pull/311)
+    @mikz
 
 ### New features
 

lib/sshkit/command_map.rb

@@ -38,14 +38,10 @@ def initialize(value = nil)
     end
 
     def [](command)
-      if prefix[command].any?
-        prefixes = prefix[command].map(&TO_VALUE)
-        prefixes = prefixes.join(" ")
+      prefixes = prefix[command].map(&TO_VALUE)
+      cmd = TO_VALUE.(@map[command])
 
-        "#{prefixes} #{command}"
-      else
-        TO_VALUE.(@map[command])
-      end
+      [*prefixes, cmd].compact.join(' ')
     end
 
     def prefix

test/unit/test_command_map.rb

@@ -30,23 +30,23 @@ def test_prefix
       map.prefix[:rake].push("/home/vagrant/.rbenv/bin/rbenv exec")
       map.prefix[:rake].push("bundle exec")
 
-      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec rake"
+      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec /usr/bin/env rake"
     end
 
     def test_prefix_procs
       map = CommandMap.new
       map.prefix[:rake].push("/home/vagrant/.rbenv/bin/rbenv exec")
       map.prefix[:rake].push(proc{ "bundle exec" })
 
-      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec rake"
+      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec /usr/bin/env rake"
     end
 
     def test_prefix_unshift
       map = CommandMap.new
       map.prefix[:rake].push("bundle exec")
       map.prefix[:rake].unshift("/home/vagrant/.rbenv/bin/rbenv exec")
 
-      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec rake"
+      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec /usr/bin/env rake"
     end
 
     def test_indifferent_setter
@@ -62,7 +62,7 @@ def test_indifferent_prefix
       map.prefix[:rake].push("/home/vagrant/.rbenv/bin/rbenv exec")
       map.prefix["rake"].push("bundle exec")
 
-      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec rake"
+      assert_equal map[:rake], "/home/vagrant/.rbenv/bin/rbenv exec bundle exec /usr/bin/env rake"
     end
 
     def test_prefix_initialization_is_thread_safe
@@ -74,5 +74,13 @@ def test_prefix_initialization_is_thread_safe
       end
       threads.each(&:join)
     end
+
+    def test_prefix_setter
+      map = CommandMap.new({})
+      map[:rake] = 'rake2.2'
+      map.prefix[:rake].push('bundle exec')
+
+      assert_equal map[:rake], 'bundle exec rake2.2'
+    end
   end
 end