## Changes
The integration test for `fs ls` tried to produce completions for the
temporary directory without a trailing slash. The command will list the
parent directory to see if there are more directories with the same
prefix that are also valid completions. The test intends to test
completions for files inside the temporary directory, so we need that
trailing slash.
This test was hanging because the parent directory of the temporary DBFS
directory has more than 1k entries (on our integration testing
workspaces) and the line buffer in the test runner has a capacity of 1k
lines. To avoid the same hang in the future, this change modifies the
test runner to panic if the line buffer is full.
## Tests
Confirmed the integration test no longer hangs.
## Changes
This PR adds autocomplete for cat, cp, ls, mkdir and rm.
The new completer can do completion for any `Filer`. The command
completion for the `sync` command can be moved to use this general
completer as a follow-up.
## Tests
- Tested manually against a workspace
- Unit tests