Getting the version for a tag without a branch fails

[cristianiorga]

[WriteVersionInfoToBuildLog] INFO Found remote tip 'refs/tags/v1.1.0^{}' pointing at the commit 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'.
[WriteVersionInfoToBuildLog] WARN Could not determine assembly version: Remote tip 'refs/tags/v1.1.0^{}' from remote 'xxx' doesn't look like a valid pull request.

Workaround: manually created a branch from the tag

[michaelnoonan]

We've also reproduced this in TeamCity with GitVersionTask 3.1.2.

Steps to reproduce:

1. Tag a commit that is not the head of any branch (in our case master)
2. Start a custom build in TeamCity for that tag
   
3. GitVersion will fail as shown above and in this log, with noise removed.

[05:01:20][Step 5/9] INFO [11/03/15 5:01:15:74] Working directory: Y:\work\refs\tags\3.2.0
[05:01:20][Step 5/9] INFO [11/03/15 5:01:15:75] Applicable build agent found: 'TeamCity'.
[05:01:20][Step 5/9] INFO [11/03/15 5:01:15:75] Branch from build environment: 
[05:01:20][Step 5/9] INFO [11/03/15 5:01:15:81] One remote found (origin -> 'https://github.com/MyOrg/MyRepo.git';).
[05:01:20][Step 5/9] INFO [11/03/15 5:01:15:81] Fetching from remote 'origin' using the following refspecs: +refs/heads/*:refs/remotes/origin/*.
[05:01:20][Step 5/9] INFO [11/03/15 5:01:18:68] Skipping update of 'refs/remotes/origin/master' as it already matches the remote ref.
[05:01:20][Step 5/9] INFO [11/03/15 5:01:18:71] Skipping update of 'refs/remotes/origin/release/3.2.0' as it already matches the remote ref.
[05:01:20][Step 5/9] INFO [11/03/15 5:01:18:71] HEAD is detached and points at commit '881258745dc3c07c64ab6cf91608ceba99a4f7ca'.
[05:01:20][Step 5/9] INFO [11/03/15 5:01:18:80] Local Refs:
[05:01:20][Step 5/9] refs/heads/master (391e7e2a161abf18405930022a65470fbfeb195d)
[05:01:20][Step 5/9] refs/heads/release/3.2.0 (ec2ca40fb8d6f9f25a49cc5edf94229a29f9c37b)
...
[05:01:20][Step 5/9] refs/remotes/origin/master (391e7e2a161abf18405930022a65470fbfeb195d)
[05:01:20][Step 5/9] refs/remotes/origin/release/3.2.0 (ec2ca40fb8d6f9f25a49cc5edf94229a29f9c37b)
...
[05:01:20][Step 5/9] refs/tags/3.2.0 (881258745dc3c07c64ab6cf91608ceba99a4f7ca)
...
[05:01:21][Step 5/9] INFO [11/03/15 5:01:18:86] No local branch pointing at the commit '881258745dc3c07c64ab6cf91608ceba99a4f7ca'. Fake branch needs to be created.
[05:01:21][Step 5/9] INFO [11/03/15 5:01:18:86] Fetching remote refs to see if there is a pull request ref
[05:01:21][Step 5/9] INFO [11/03/15 5:01:20:85] Remote Refs:
[05:01:21][Step 5/9] HEAD
[05:01:21][Step 5/9] refs/heads/master
[05:01:21][Step 5/9] refs/heads/release/3.2.0
...
[05:01:21][Step 5/9] refs/pull/11/head
[05:01:21][Step 5/9] refs/pull/11/merge
...
[05:01:21][Step 5/9] refs/tags/3.2.0
...
[05:01:21][Step 5/9] refs/tags/build-2.0.0.79
[05:01:21][Step 5/9] refs/tags/build-2.0.0.79^{}
[05:01:21][Step 5/9] refs/tags/build-2.0.0.84
[05:01:21][Step 5/9] refs/tags/build-2.0.0.84^{}
...
[05:01:21][Step 5/9] INFO [11/03/15 5:01:20:85] Found remote tip 'refs/tags/3.2.0' pointing at the commit '881258745dc3c07c64ab6cf91608ceba99a4f7ca'.
[05:01:21][Step 5/9] WARN [11/03/15 5:01:20:86] An error occurred:
[05:01:21][Step 5/9] Remote tip 'refs/tags/3.2.0' from remote 'https://github.com/MyOrg/MyRepo.git'; doesn't look like a valid pull request.

We can see GitVersion is trying to create a temporary branch, but gets distracted looking for pull requests.

Workaround: we ended up just moving our tag to the head of master, so a similar workaround to @cristianiorga

Running locally with GitVersion.Portable 3.3.0:

INFO [11/03/15 15:36:50:66] Using latest commit on specified branch
INFO [11/03/15 15:36:53:06] Running against branch: (no branch) (c5ef47a8a7f79e06bb011ef538a3c08f3f9bb380)
WARN [11/03/15 15:36:53:08] An error occurred:
 looks like the branch being examined is a detached Head pointing to commit 'c5ef47a'. Without a proper branch name GitVersion cannot determine the build version.

[JakeGinnivan]

The normalisation should just bail if building a tag because we don't do version calculations anyways if a commit is tagged. Hopefully a simple fix