Enable Syncthing automatic startup on login in macOS

syncthing.sh

#!/bin/bash

#----------------------------------------------------
#
# Copyright (C) 2017 Vlad Didenko
#
# This Source Code Form is subject to the terms
# of the Mozilla Public License, v. 2.0. If a copy
# of the MPL was not distributed with this file,
# You can obtain one at https://mozilla.org/MPL/2.0/
#
#----------------------------------------------------

# InstallDir is where the Syncthing software was copied to.
# To use the browser-based software update feature this folder
# and files in it should be writeable by the user running the
# Synching.
InstallDir=/Applications/Syncthing

# A directory dedicated for Syncthing logs
LogDir=${HOME}/Library/Logs/Syncthing

# LaunchAgent location 
LaunchAgentDir=${HOME}/Library/LaunchAgents

# Launch Agent file name
LaunchAgentFile=local.syncthing.plist

# ServiceId is the identifier used by the launchd  and launchctl
ServiceId=local.syncthing

#   End of configuration
#
#############################

laf=${LaunchAgentDir}/${LaunchAgentFile}

function WriteLaunchAgent {
	if [ -f "${laf}" ]
	then
		echo LaunchAgent file already exists at \"${laf}\". Please, review the file and delete it if nesessary before running this installation. 1>&2
		exit 1
	fi

cat > ${laf} <<EndPlist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
	<dict>
		<key>Label</key>
		<string>${ServiceId}</string>

		<key>ProgramArguments</key>
		<array>
			<string>${InstallDir}/syncthing</string>
			<string>-no-browser</string>
		</array>

		<key>KeepAlive</key>
		<true/>

		<key>ThrottleInterval</key>
		<integer>60</integer>

		<key>LowPriorityIO</key>
		<true/>

		<key>ProcessType</key>
		<string>Background</string>

		<key>StandardOutPath</key>
		<string>${LogDir}/Syncthing.out.log</string>

		<key>StandardErrorPath</key>
		<string>${LogDir}/Syncthing.err.log</string>

	</dict>
</plist>
EndPlist
}

function DeleteLaunchAgent {
	if [ ! -f "${laf}" ]
	then
		echo LaunchAgent file not found at \"${laf}\". Nothing to remove. 1>&2
		exit 1
	fi

	rm "${laf}"
}

case ${1} in
enable)
	WriteLaunchAgent
	;;
disable)
	DeleteLaunchAgent
	;;
start)
	launchctl load "${laf}"
	;;
stop)
	launchctl unload "${laf}"
	;;
*)
	echo Allowed commands are: enable, disable, start, and stop. 1>&2
	exit 1
esac

A [slightly] more convenient Syncthing method than documented at https://docs.syncthing.net/users/autostart.html#macos