BLT deploys are failing with a "tag already exists" message

Issue

BLT deployments are running into a fatal error related to creating an already existing tag in the source repository:

fatal: tag 'new-tag' already exists
...
[error] Failed to create Git tag!
...
For troubleshooting guidance and support, see https://docs.acquia.com/blt/support/
...
ERROR: Job failed: exit code 1

Resolution

Setting the 'deploy.tag_source' value in your BLT configs to "False" will allow BLT to skip the tag creation process in the source repository, which should allow the deployment to continue past that step.