"Legacy" is the layout used in maven 1 repositories while maven 2 uses "default". They are different in terms of directory structure, timestamp of snapshots in default and existence of metadata files in default.
groupId |--artifactId |--jars `--artifact
groupId |--artifactId |--version | `---artifact |---metadata
In able to deploy an artifact in a legacy layout of repository, set the repositoryLayout parameter to legacy value.
mvn deploy:deploy-file -Durl=file:///C:/m2-repo \ -DrepositoryId=some.id \ -Dfile=your-artifact-1.0.jar \ -DpomFile=your-pom.xml \ -DrepositoryLayout=legacy