Cocoapods error: "Pull is not possible because you have unmerged files."
Problem was with specs repository, not on my side.
Found the answer here podfile gives an error on install, but since the question was less explicit on the symptom, I thought I would cross-reference it again in case someone was looking it up differently.
The answer is in the blog post here http://blog.cocoapods.org/Repairing-Our-Broken-Specs-Repository/ which explains the issue and the fix which is repeated below:
"You are going to have to manually delete any local copies of the Specs repository and re-clone the new version of the Specs repository. You can do that with the following commands:
$ pod repo remove master $ pod setup
If you have any local commits or changes to the Specs repository which are not merged, you should ensure you have a copy of them. I would recommend that you manually copy these changes over and re-commit them. You can fix your repository without deleting, however, this is not a simple process, so we are instead recommending that you delete your copy of the Specs repository and any forks of it."