id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
18588	Comply with OSM Tile Usage Policy	simon04	team	"JOSM violates the OSM Tile Usage Policy https://operations.osmfoundation.org/policies/tiles/

> DO NOT send no-cache headers. (`Cache-Control: no-cache`, `Pragma: no-cache` etc.)

JOSM sends both headers

{{{
GET /11/1085/719.png HTTP/1.1
User-Agent: JOSM/1.5 (15736 SVN en_GB) Linux Arch Linux Java/11.0.6
Cache-Control: no-cache
Accept: text/html, image/png, image/jpeg, image/gif, */*
Accept-Encoding: gzip
If-None-Match: ""2ab5b55b0b85f4445b940246b7cac567""
Pragma: no-cache
Host: b.tile.openstreetmap.org
Connection: keep-alive
If-Modified-Since: Mon, 20 Jan 2020 19:51:08 GMT
}}}

The behaviour has been introduced in r9228. According to that commit message,
> This avoids getting objects from Java Web Start Cache…

We have a few options:
1. Drop the `no-cache` headers altogether
2. Keep `no-cache` only for Java Web Start (detect via `org.openstreetmap.josm.actions.ShowStatusReportAction#isRunningJavaWebStart`)
3. Exclude `tile.openstreetmap.org`"	defect	closed	major	20.01	Core imagery		fixed