In testing for Cros move to using Isolate, I ran an upload of a dummy directory to be sure I could replicate it. This was possible both with the Go tools and with the Python tools, but only the Python tools printed the hash where the upload could be found. Output below:

jkop@jkop:~/chromiumos/src/third_party/autotest/files$ isolated archive -dirs :dummy
[found] [hashed/size/to hash] [looked up/to lookup] [uploaded/size/to upload/size]
Hits    :     0 (0b)
Misses  :     0 (0b)
Duration: 2ms
[I2018-07-25T15:14:36.670569-07:00 65860 0 archiver.go:627] Looked up 4 items

jkop@jkop:~/chromiumos/src/third_party/autotest/files$ 
jkop@jkop:~/chromiumos/src/third_party/autotest/files$ ~/browser_infra/infra/luci/client/isolateserver.py archive dummy/
7bdc91f6940a76570ca6e0e8965a08a706a9562d dummy/
jkop@jkop:~/chromiumos/src/third_party/autotest/files$