When I had to work on multiple Java projects on different branches & releases, I noticed that the M2_REPO entry in eclipse was marked as non modifiable.
This is the M2Eclipse, Maven plugin for Eclipse at work. The settings.xml which sets it is specified in Eclipse under preferences->maven->user settings
However, to have different M2REPO entries for different projects, you have two options
- Remove M2Eclipse & manually set M2_REPO entries for each project, so they get saved with the project
- Before running Eclipse for each project, modify the settings.xml pointed to in above m2Eclipse user settings to set a different M2_REPO using