file sync up: Cannot upload files when -local-path is just a name of a file or folder

[watermint]

$ ./tbx file sync up -local-path tbx-73.2.565.zip -dropbox-path /2020-08-31

watermint toolbox 73.0.20200828031906
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Testing network connection...
Trying...
Done


| upload_start                        | upload_end                          | num_bytes | num_files_error | num_files_upload | num_files_skip | num_api_call |
|-------------------------------------|-------------------------------------|-----------|-----------------|------------------|----------------|--------------|
| 2020-08-31T18:17:19.378080123+09:00 | 2020-08-31T18:17:19.378433055+09:00 | 0         | 1               | 0                | 0              | 0            |

Log

{"level":"DEBUG","time":"2020-08-31T18:17:19.378+0900","name":"z888.z890.z1035","caller":"file/upload_worker.go:43","msg":"unable to calculate rel path","dropboxBasePath":"/2020-08-31","localBasePath":"tbx-73.2.565.zip","localFilePath":"tbx-73.2.565.zip","error":"target path is shorter than base path"}