Jenkins LTS 1.509.3 provides Credentials plugin version 1.3.1.
Jenkins 1.534 provides Credentials plugin version 1.4.

Recent versions of the git-client plugin (at least 1.3.0) depend on the ssh-agent plugin which itself requires version >=1.6 of the Credentials plugin though, otherwise it's failing with:

FATAL: com/cloudbees/plugins/credentials/common/StandardCredentials
java.lang.NoClassDefFoundError: com/cloudbees/plugins/credentials/common/StandardCredentials
at org.jenkinsci.plugins.gitclient.Git$1.invoke(Git.java:62)
[...]

Manually updating the credentials plugin in an automated fashion doesn't seem to be possible (when placing http://updates.jenkins-ci.org/latest/credentials.hpi inside the plugin directory then on Jenkins restart the built-in credentials plugin seems to always get restored to its old/built-in version).

AFAICS there's no way to update a built-in plugin besides using the web interface with its plugin manager (neither the credentials.hpi nor the Jenkins cli API way work for me). This hurts quite a lot because there's no way to automatically install recent versions of the git-client plugin any longer.

Possible solutions:

• Update Credentials plugin in LTS + latest versions
• Avoid strict dependency on ssh-agent in git-client plugin
• Avoid strict dependency on Credentials plugin >=1.6 in ssh-agent plugin
• Provide a way how to update the Credentials plugin in an automated fashion (like 'wget http://updates.jenkins-ci.org/latest/credentials.hpi') [did I miss here something?]

Any ideas/feedback?