Clients receiving an HTTP 301 Moved Permanently may conservatively
change the method of a POST request to GET.
The newer HTTP 307 Temporary Redirect and 308 Permanent Redirect
explicitly allows retrying POST requests after the redirect.
These should be safe for ServeMux as this internal redirect is generated
before user provided handlers are called.
As ServeMux is making the redirect for the user without explicit
direction, and clients may cache Permanent Redirects indefinitely,
Temporary Redirect is used in case the user adds a handler for a path,
that was previously redirected but no longer should.
Fixes #50243
Fixes #60769
Change-Id: I6c0b735bab03bb7b50f05457b3b8a8ba813badb2
Reviewed-on: https://go-review.googlesource.com/c/go/+/720820
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Damien Neil <dneil@google.com> Reviewed-by: Mark Freeman <markfreeman@google.com>