Merge branch 'ew/http-alternates-as-redirects-warning' into maint

Recent versions of Git treats http alternates (used in dumb http transport) just like HTTP redirects and requires the client to enable following it, due to security concerns. But we forgot to give a warning when we decide not to honor the alternates. * ew/http-alternates-as-redirects-warning: http: release strbuf on disabled alternates http: inform about alternates-as-redirects behavior