hgview #3430 manage group of users [validation pending]

It would be nice to be able to create groups of users and assign a specific color to each of them

I see 3 immediate uses :

• for small projects : handles nicely authors commiting from several accounts with different identity
• for large groups (eg linux kernel) identifies authors working on the same subset of a project
• allow stability of color assignment when more developpers come into a project