While calling the git client from within the ssh agent's scope it is giving "script returned exit code 128" error 

stage ('Prune git tags') 
{            
 steps {              
   sshagent(['Credential_ID']) 
    {                
     sh ''' 
     git tag --list | xargs git tag --delete && git fetch --tags
     '''              
     }      
  }
} 

Upon adding 

Host *.stie.com  StrictHostKeyChecking no  UserKnownHostsFile /dev/null 

Jenkins builds started passing but for GitHub

Host github.com  StrictHostKeyChecking no  UserKnownHostsFile /dev/null 

it is still failing the build.

For me adding a host key entry in every call is difficult. Can I add something like global host key and pass them in sshagent globally, I have already added them for internal SCM Urls for git calls. But somehow they are not being passed under the sshagent scope calls on slave node.