test if local commands are present and log if not, helps to debug pro…

…blems with e.g. git not in $PATH

lib/capistrano/recipes/deploy.rb

@@ -94,9 +94,18 @@ def with_env(name, value)
 # returns the command output as a string
 def run_locally(cmd)
   logger.trace "executing locally: #{cmd.inspect}" if logger
+  command_present?(cmd)
   `#{cmd}`
 end
 
+# tests if the given command is present on the local system
+def command_present?(cmd)
+  executable = cmd.to_s.split(" ").first
+  unless system("which #{executable}")
+    logger.important "executable '#{executable}' not present or not in $PATH on the local system!"
+  end
+end
+
 # If a command is given, this will try to execute the given command, as
 # described below. Otherwise, it will return a string for use in embedding in
 # another command, for executing that command as described below.