mvn dependency:unpack via CLI generates ${project.basedir} folder

Steps to reproduce

1. Get a sample dependency first

mvn dependency:get -DgroupId=org.apache.ant -DartifactId=ant -Dversion=1.8.3 -Dpackaging=jar

2. Delete the file ~/.m2/repository/org/apache/ant/ant/1.8.3/_remote.repositories
3. Unpack the dependency somewhere

cd /tmp
mkdir unpack
mvn dependency:unpack -Dartifact=org.apache.ant:ant:1.8.3:jar -DoutputDirectory=./unpack

4. Observe that ${project.basedir} was created

$ ls -l /tmp/unpack

total 0
... ${project.basedir}
... unpack

Note Step 2 is only necessary because of getting the dependency, this wouldn't have to be done if it had been installed. This doesn't affect whether the bug occurs or not.

Workarounds

The closest would be to use mvn dependency:copy and then unpack manually through a subsequent command. Interestingly this shows that the bug doesn't affect mvn dependency:copy.

Similar/related issues (their fixes don't apply here):

• https://stackoverflow.com/q/11669446/321797
• https://netbeans.org/bugzilla/show_bug.cgi?id=221560