See http://jenkins.361315.n4.nabble.com/Users-unicity-td2542625.html for related discussion.

Jenkins is missing a way to ensure users unicity since they are created from various sources: authentication method (LDAP in my case), code commits (Subversion, Mercurial, Git, ...).
Depending on the way the user is retrieved by Jenkins (from a commit on a given SCM or its authentication), multiple identities are created for the same real user.
As a consequence, some features are not fully or badly working (login, notifications, user's builds, continuous integration game, ...) and configuration of users is a pain as it must be done multiple times for each real user.

Wanted features are:

• a merging feature. Allow to merge multiple Jenkins users into a single account.
• a user pattern per SCM. Allow to choose how to extract a username from a commit for each SCM and how to optionally match existing one instead of creating a new user.
• an id pattern per notification type. Allow to define how to generate the default id used for notification from the user data (from his jenkins id, his name, his scm id, ...): for instance his mail or his jabber id, ...