Clone hangs when done over http with --reference

I have a reproducible case where git clone --reference hangs when performed over http://, but not when performed over git://

The repository in question is very large, which possibly plays a role in this. Unfortunately, I was not able to reproduce this with any other repository, so if anyone wants to try this, they will have to suffer through 2.5GB downloads.

To reproduce on the client:

git clone --mirror \ http://source.codeaurora.org/mirrors/chromium.googlesource.com/chromium/src (completes after downloading ~2.5GB)

git clone --reference ./src.git --mirror \ http://source.codeaurora.org/quic/chrome4sdp/chromium/src.git foo.git (this hangs forever)

If you do this over git:// protocol, it will work:

git clone --reference ./src.git --mirror \ git://source.codeaurora.org/quic/chrome4sdp/chromium/src.git foo.git (completes after downloading ~100MB)

It will also work if you clone the same repo without --reference. Both repositories pass fsck checks.

I reproduced it with git-2.4.0 on the server, and it appears to be unrelated to the Apache/Nginx versions nor various httpd daemon settings, at least not in my testing. No errors are generated in the logs. The process just appears to be stuck not doing anything.

To reproduce locally, simply set up these two repositories in /var/lib/git (one can be a --reference clone of the other -- it didn't matter in my tests), and put this in /etc/httpd/conf.d/git.conf, assuming Fedora or Centos7 system:

SetEnv GIT_PROJECT_ROOT /var/lib/git SetEnv GIT_HTTP_EXPORT_ALL 1

AliasMatch ^/git/(.*/objects/[0-9a-f]{2}/[0-9a-f]{38})$ /var/lib/git/$1 AliasMatch ^/git/(.*/objects/pack/pack-[0-9a-f]{40}.(pack|idx))$ /var/lib/git/$1

ScriptAlias /git/ /usr/libexec/git-core/git-http-backend/

<Directory "/var/lib/git">
    AllowOverride None
    Options None
    Require all granted
</Directory>
<Directory "/usr/libexec/git-core">
    AllowOverride None
    Options None
    Require all granted
</Directory>

Not sure what is going on, but it appears that the hang is on the server. Hope someone can figure it out.

Best,