if we use a tag in the branch configuration, it seems to break the check out. We use tags in our deployment steps, whereas a user would like to deploy a specific version (using maven). To do that, we need to check out a specific tag and run "mvn deploy" on it. This worked in 1.37 but it does not work in 1.41. We have backed the version of the plugin to get around this problem.

Steps to reproduce:

1. Create a free style job (any job type will do)
2. Configure the mercurial plugin to clone a repository and instead of set a branch, set hg TAG on it
3. Start the build

Expected result:
The code is checked out as it looked like when the tag was set

Actual result:
We get this error in the console

Started by user anonymous
Building on master in workspace /proj/hudson/home/project/jobs/some_job/workspace

Deleting project workspace... done

$ hg clone --rev rel-3.4.19.0 --noupdate /some/repo /proj/hudson/home/project/jobs/some_job/workspace
adding changesets
adding manifests
adding file changes
added 5311 changesets with 14365 changes to 3636 files
[workspace] $ hg update --rev rel-3.4.19.0
abort: unknown revision 'rel'!
ERROR: Failed to update /some/repo to rev rel-3.4.19.0
some_job is disabled. Triggering skipped
Finished: FAILURE