Incorrect description of Pkg.gc --all flag?

[albheim]

In the readme it is mentioned that

One option for a more deep cleaning is to run ]gc --all, but this will remove... well... all packages.

which does not seem true according to the help string, and when trying it I still have plenty of packages left.

(@v1.9) pkg> ?gc
  gc [-v|--verbose] [--all]


  Free disk space by garbage collecting packages not used for a significant time. The
  --all option will garbage collect all packages which can not be immediately reached
  from any existing project. Use verbose mode for detailed output.

With that said, nice package. I run gc quite often but still have a huge julia folder, but this helped me select a couple of old things I wanted to keep around, but probably not run, so the gc could clean them up.