Jenkins + git: "tell me who you are" error, why does it need to tag?

The idea of tagging when pulling/cloning a repo is common to most Build Scheduler out there:
Hudson-Jenkins, but also CruiseControl (The build label determined by the labelincrementer), or RTC Jazz Build Engine (where they are called "snapshots").

The idea is to set a persistent record of the input to a build.
That way, the code you are pulling, even if it wasn't tagged, is tagged automatically for you by the build scheduler, in order to be able to get back to that specific build later.

If that policy (always tagging before a build) is set, then Jenkins will need to know who you are in order to make a git tag (it is a git object with an author attached to it: user.name and user.email).

However, as mentioned in " Why hudson/jenkins tries to make commit? ":

Checks "Skip internal tag" config under "Advanced..." in section "Source code management".

That should avoid that extra tagging step you appear to not need.

As for how to set user.email and user.name, In jenkins, go to "Manage Jenkins" > "Configure System" and scroll down to "Git plugin" and there you will find

enter your email and name, you're good to go.