changes in the default configuration do not propagate to the upgrades of earlier go-ipfs versions

Version information

go-ipfs version: 0.4.5-
Repo version: 5
System version: amd64/windows
Golang version: go1.7.4

Type: bug (misconfiguration)

Priority: ?

Description

The chat log from fedwiki/wiki-client#173 says that changes in the default configuration of go-ipfs do not automatically apply to users of earlier versions when they upgrade. Click to enlarge:

It means that earlier adopters do not automatically get config-related features (such as CORS from #2778) and it makes those features less reliable.

For example, I cannot reliably host a 360°×180° photo for a Pannellum-based panorama on IPFS (unless I decide to achieve “same origin” by putting the whole engine of Panellum on IPFS as well, but that would be quite a 無駄) because:

• Panellum would use that photo as a WebGL texture,

• WebGL textures are CORS-controlled,

• some of IPFS users install Firefox addons or Chrome extensions to redirect IPFS requests to their local gateways,

• their local gateways won't automatically have CORS unless they're v0.4.3-rc4 (or later) and a clean installation (not an upgrade) or users edited their configurations manually to enable CORS (the latter's not likely because why would they know to do that).

Something should be done about it. Consider, for example, two separate configuration files (one for the default config and the other for the overrides of the defaults).