Core support for private vs. public projects
Starting with this version, projects are either public or private. Public projects are always visible for everybody (except anonymous users if you force authentication - obviously). Private projects are visible only for the users and groups who are listed on their "Permissions" page.
To decide whether a given project should be made public or private, the migration relies on the permissions granted to the virtual "Anyone" group. If "Anyone" has the "Browse" and "See Source Code" permission, then the project is set to public - otherwise it's set to private.
Once the migration is done, you might want to double-check your projects to make sure that their visibility match your expectations.
File encoding auto-detection
Originally, SonarQube scanners used the value of the sonar.sourceEncoding property to read all files in a module. SonarQube 6.2 improved this: files with a BOM are processed using the encoding specified by the BOM, regardless of the value of sonar.sourceEncoding. SonarQube 6.4, goes a little further: for files without a BOM, heuristics are applied to detect well known encodings. Failing that, the configured sonar.sourceEncoding is used as a fallback. The goal is that most projects are processed correctly out of the box, without needing extra configuration.
The default group "sonar-users" can no longer be updated manually (new users are still added automatically) and cannot be deleted ( SONAR-9022 - Prevent updating default user groupClosed).