It would be nice to have a simple and generic way for build steps to find out what plugins are installed. For example, shell build steps could enable ANSI color output for the tools they call if the ansicolor plugin [1] was installed, or they could disable timing in the tools they call if the timestamper plugin [2] was installed.

A simple and generic way to allow for this would be to add a "JENKINS_PLUGINS" variable to the list at [3], set to a whitespace separated list of plugin IDs for all installed plugins. A build step could then check that environment variable for a plugin ID and take actions accordingly.

[1] https://wiki.jenkins-ci.org/display/JENKINS/AnsiColor+Plugin
[2] https://wiki.jenkins-ci.org/display/JENKINS/Timestamper
[3] https://wiki.jenkins-ci.org/display/JENKINS/Building+a+software+project#Buildingasoftwareproject-JenkinsSetEnvironmentVariables