Tweaks to once command and docs

[invisig0th]

No description provided.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.11% ⚠️

Comparison is base (06a21aa) 97.31% compared to head (1382d33) 97.21%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3282      +/-   ##
==========================================
- Coverage   97.31%   97.21%   -0.11%     
==========================================
  Files         227      227              
  Lines       45437    45432       -5     
==========================================
- Hits        44216    44165      -51     
- Misses       1221     1267      +46     

Flag	Coverage Δ
linux	97.21% <100.00%> (-0.01%)	⬇️
linux_replay	?

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Files Changed	Coverage Δ
synapse/lib/storm.py	95.69% <100.00%> (-0.01%)	⬇️

... and 9 files with indirect coverage changes

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