I solved the issue on my side (running maven 3.0.5) by updating the git scm provider dependency, not the release plugin version:
<build>
<plugins>
<plugin>
<artifactId>maven-release-plugin</artifactId>
<version>2.4.2</version>
<dependencies>
<dependency>
<groupId>org.apache.maven.scm</groupId>
<artifactId>maven-scm-provider-gitexe</artifactId>
<version>1.8.1</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
The git scm 1.8.1 version correctly makes the git commit (tested with the prepare and rollback goals).
EDIT: Different versions of maven-release-plugin and maven-scm-provider-gitexe may be required depending on your environment. See the comments for more discussion.