ensuring correct git branch before "pulling"

Rather than performing a git pull, (which merges the desired branch into the current one, even if they aren't the same), this ensures the repo is on the correct branch before merging.
Fixes bevry#7

src/lib/safeps.coffee

@@ -882,7 +882,14 @@ safeps =
  safefs.ensurePath opts.cwd, (err,exists) ->
  return complete(err) if err
  if exists
- safeps.spawn ['git', 'pull', opts.remote, opts.branch], opts, (err,result...) ->
+ # this ensures the repo is on the correct branch before performing a merge or fast-forward
+ commands = []
+ commands.push ['git', 'fetch', opts.remote]
+ commands.push ['git', 'checkout', opts.branch]
+ commands.push ['git', 'merge', "#{opts.remote}/#{opts.branch}"]
+
+ # Perform commands
+ safeps.spawnMultiple commands, opts, (err,result...) ->
  return next(err, 'pull', result)
  else
  safeps.initGitRepo opts, (err,result) ->