To unify your fish shell history:

• Install plentys on the host of your choice.
• Install plenty on your machines.
• Run plenty <host> periodically on your machines.

Simple tools in Rust, communicating over SSH in a binary protocol (TLV).

plenty is the client, invoked with plenty <host>. plentys is the server, invoked by the client through ssh <host> plentys.

1. Create .local/share/plenty on the server if it doesn't exist.
2. Create .local/share/plenty/history.db on the server if it doesn't exist, with the following schema:

"CREATE TABLE IF NOT EXISTS history (
  cmd TEXT,
  "when" INTEGER,
  extra TEXT
)

CREATE UNIQUE INDEX IF NOT EXISTS idx_history_unique
ON history("when", cmd, extra)

3. Take a lock on ~/local/share/fish using flock(LOCK_SH|LOCK_EX) on the client.
4. Read ~/.local/share/fish/fish_history on the client.
5. INSERT OR IGNORE INTO history on the server.
6. Select the full history on the server ORDER BY "when", send it to the client.
7. Write it to ~/.local/share/fish/fish_history on the client.
8. Release the lock on the client.