Comparison function for If-Match and If-None-Match

[mnot@…]

In the definitions of If-Match and If-None-Match, we don't specify whether the weak or strong comparison function is to be used when these validations actually occur, although we spend a lot of text on when to use weak vs. strong ETags themselves.

Now, you might say that an origin server can decide whether to use the weak or strong function, but an intermediary or client cache doesn't have license to do weak comparison, and could cause a lot of trouble if it did. AFAICT we don't specify this, but I think we should.

[mnot@…]

Resolution: both should be explicitly using the weak comparison function.

[fielding@…]

From [2131]:

clarify that If-Match and If-None-Match use the weak comparison function, since otherwise weak etags would never work; addresses #402