Add withMerge flag for gitSSHCheckout step

Rather than merge the changes to be built into a branch which
tracks the remote I want to push to, it checks out one rev and
merges the others on, resulting in a detached HEAD.

Some tools expects to be run on a specific branch, and it
fails because the repo isn't in that state.

[1]. https://issues.jenkins-ci.org/browse/JENKINS-6856

Change-Id: I9d6e2caf639d1aba651ae5f709c6369ea2848546
2 files changed
tree: 5be347dcde2ad236332966de0027a2e0a8c679c1
  1. src/
  2. vars/
  3. .gitreview