Well, to answer my own question...
I was mostly successful by simply creating a new (empty) eclipse workspace and make sure that the Preferences->Java->Installed JREs actually points at your JDK, and not the JRE. (otherwise nothing will compile)
Then create a new project with the wizard.
File->New->Other...->Maven->Checkout Maven Projects from SCM
Click "Next..." and the Target Location selector appears. Choose "git" in the SCM type selector, then enter the URL for the git repository. (https://git-wip-us.apache.org/repos/asf/flume.git)
Click "Finish" and eclipse (+ m2eclipse) handles checking out the Flume trunk and creating all of the projects.
A couple problems remain in the POM files, though.
In flume-ng-sdk/pom.xml and the flume-avro-source/pom.xml, Eclipse is showing errors in the definition of the avro-maven-plugin and the paranamer-maven-plugin. In each it says,
Plugin execution not covered by lifecycle configuration: org.apache.avro:avro-maven-plugin:1.6.1:idl-protocol (execution: default, phase: generate-sources)
I can guess what the error means, but I have no idea how to fix it.
From: DeCarlo, Thom [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, December 18, 2012 8:55 AM
To: [EMAIL PROTECTED]
Subject: Question about the Setting up Eclipse wiki page
On the wiki, https://cwiki.apache.org/confluence/display/FLUME/Development+Environment#DevelopmentEnvironment-SettingupEclipse, the basic instructions say that I can use either the maven-eclipse plugin or the m2eclipse plugin. But, it only shows how to use the maven-eclipse plugin. Are the instructions the same for m2eclipse? The implication that I get from the page is no.