libstore: remove github etag workaround

this was a workaround for a *github* bug that happend *in 2015*.
not only is github no longer buggy, it shouldn't have been nix's
responsibility to work around these bugs like this to begin with

while we're at it we'll also remove another workaround—again for
github specifically and again for etag handling—from 2021 that's
also not needed any more. future workarounds for serverside bugs
should probably come with an expiration date that mutates into a
build warning after a while, otherwise this *will* happen again.

Change-Id: I74f739ae3e36d40350f78bebcb5869aa8cc9adcd

1 files changed, 0 insertions, 23 deletions

diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index 7d36796f4..adbeb58ca 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -204,17 +204,6 @@ struct curlFileTransfer : public FileTransfer
 
                     if (name == "etag") {
                         result.etag = trim(line.substr(i + 1));
-                        /* Hack to work around a GitHub bug: it sends
-                           ETags, but ignores If-None-Match. So if we get
-                           the expected ETag on a 200 response, then shut
-                           down the connection because we already have the
-                           data. */
-                        long httpStatus = 0;
-                        curl_easy_getinfo(req, CURLINFO_RESPONSE_CODE, &httpStatus);
-                        if (result.etag == request.expectedETag && httpStatus == 200) {
-                            debug("shutting down on 200 HTTP response with expected ETag");
-                            return 0;
-                        }
                     }
 
                     else if (name == "content-encoding")
@@ -375,24 +364,12 @@ struct curlFileTransfer : public FileTransfer
                 }
             }
 
-            if (code == CURLE_WRITE_ERROR && result.etag == request.expectedETag) {
-                code = CURLE_OK;
-                httpStatus = 304;
-            }
-
             if (writeException)
                 failEx(writeException);
 
             else if (code == CURLE_OK && successfulStatuses.count(httpStatus))
             {
                 result.cached = httpStatus == 304;
-
-                // In 2021, GitHub responds to If-None-Match with 304,
-                // but omits ETag. We just use the If-None-Match etag
-                // since 304 implies they are the same.
-                if (httpStatus == 304 && result.etag == "")
-                    result.etag = request.expectedETag;
-
                 act.progress(result.bodySize, result.bodySize);
                 done = true;
                 callback(std::move(result));