Fish history deduplication

dedup_history.fish

function dedup_fish_history --description "Deduplicate Fish shell history (compatible with old/new versions)"
    # 1. Get the path to the history file in a backwards-compatible way.
    set -l histfile
    # Try the modern way first.
    if command -q fish_config && fish_config path history >/dev/null 2>&1
        set histfile (fish_config path history)
    else
        # Fall back to the legacy default path for older fish versions.
        set histfile "$HOME/.local/share/fish/fish_history"
        # Some very old versions might use ~/.fish_history
        if not test -f "$histfile"
             set histfile "$HOME/.fish_history"
        end
    end

    if not test -f "$histfile"
        echo (set_color red)"History file could not be found."(set_color normal)
        return 1
    end

    # 2. Create a timestamped backup for safety.
    set -l backup_file "$histfile.bak."(date +%F-%T)
    cp -p "$histfile" "$backup_file"
    echo "↪ Safety backup created at:" (set_color blue)$backup_file(set_color normal)

    # 3. Use a secure temporary file for the new history.
    set -l temp_file (mktemp)

    # 4. The core logic (this part remains the same).
    echo "Deduplicating..."
    tac "$histfile" | awk '
        /^-\scmd:\s/ {
            cmd = substr($0, 8)
            if (!seen[cmd]++) {
                if (prev_line ~ /^\s+when:\s/) {
                    print prev_line
                }
                print $0
            }
        }
        { prev_line = $0 }
    ' | tac > "$temp_file"

    # 5. Calculate stats.
    set -l old_count (math (string trim --right (wc -l < "$backup_file")) / 2)
    set -l new_count (math (string trim --right (wc -l < "$temp_file")) / 2)

    # 6. Replace the original history file.
    mv "$temp_file" "$histfile"

    # 7. Reload the history for the current session.
    history clear-session
    history merge

    echo (set_color green)"✅ History deduplicated successfully."(set_color normal)
    echo "   Commands before: " (string trim $old_count)
    echo "   Commands after:  " (string trim $new_count)
    echo "   Commands removed:" (string trim (math $old_count - $new_count))
end