Gulp-concat and gulp-rename: file.dirname not working

Question

I'm currently using gulp concat to concatenate every js file in a root/**/js directory, and i want to move them in another folder. I was using the file.dirname of gulp-rename to ensure that my destination folder would match the /**/ of the source, except that concat seems to overwrite this somehow because file.dirname doesn't give the proper name ( it's replaced by a "." ) Do you guys know any ways i could use concat and rename at the same time ? The destination folder have to match the /**/ directory name of the source