Bug 1237395

Clones were seen to be taking a *really* long time.  When I strace git (git-remote-https as it ends up being) I saw

---
$ git clone https://git.openstack.org/openstack-infra/system-config
...
4606  1435711642.024680 recvfrom(3, "\27\3\1\0 ", 5, 0, NULL, NULL) = 5
4606  1435711642.024715 recvfrom(3, "H\325\v>8\236A\277;\250K\365\33$W\1\302,M\23\\\ro\212%\321\335\6\357T\326\365", 32, 0, NULL, NULL) = 32
4606  1435711642.024791 select(0, [], [], [], {0, 50000}) = 0 (Timeout)
4606  1435711642.075059 poll([{fd=3, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 1 ([{fd=3, revents=POLLIN|POLLRDNORM}])
4606  1435711642.075166 recvfrom(3, "\27\3\1\0`", 5, 0, NULL, NULL) = 5
4606  1435711642.075210 recvfrom(3, "=\232\353\276@@\6\2\221wX\225\30\262\221\204\361\251M)\244\3602;\354\3674S\2776\233&"..., 96, 0, NULL, NULL) = 96
4606  1435711642.075306 poll([{fd=3, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 1 ([{fd=3, revents=POLLIN|POLLRDNORM}])
4606  1435711642.075346 recvfrom(3, "\27\3\1\0 ", 5, 0, NULL, NULL) = 5
4606  1435711642.075379 recvfrom(3, "\370\300\\\373\250N\375\30n]\205\371\16\372L\373\36;]W\237L\214\364\325\374\234\301^\237\31\5", 32, 0, NULL, NULL) = 32
4606  1435711642.075437 select(0, [], [], [], {0, 50000}) = 0 (Timeout)
---

I didn't wait for it to finish because apparently it ends up taking about 40 minutes.

Comparing this to a "bare" curl call for the same thing, i.e.

---
$ curl -o /dev/null -H 'Pragma: no-cache'-v https://git.openstack.org/openstack-infra/system-config/info/refs?service=git-upload-pack
---

it goes *way* faster, a few seconds.  The strace there looks *almost* the same, but the telling difference is the lack of select() calls

---
4679  1435711687.733287 recvfrom(3, "\27\3\1\0 ", 5, 0, NULL, NULL) = 5
4679  1435711687.733319 recvfrom(3, "<~\t$D+\353\245\341\223\303x\374\232\343+aMd\363\200|\307R\3m\211,i\22\336\\", 32, 0, NULL, NULL) = 32
4679  1435711687.733379 stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
4679  1435711687.733427 poll([{fd=3, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 1000) = 1 ([{fd=3, revents=POLLIN|POLLRDNORM}])
4679  1435711687.733459 poll([{fd=3, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 1 ([{fd=3, revents=POLLIN|POLLRDNORM}])
4679  1435711687.733493 recvfrom(3, "\27\3\1\0 ", 5, 0, NULL, NULL) = 5
4679  1435711687.733524 recvfrom(3, "\275\20\200[\225\232\245\374n\24)\361\20\312\204\375\377T\227\220\315\\\344\3211\344^\251\266I\216\237", 32, 0, NULL, NULL) = 32
4679  1435711687.733579 stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
4679  1435711687.733627 poll([{fd=3, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 1000) = 1 ([{fd=3, revents=POLLIN|POLLRDNORM}])
4679  1435711687.733659 poll([{fd=3, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 1 ([{fd=3, revents=POLLIN|POLLRDNORM}])
---

It was also noticed that 1.8 git doesn't do this.  So I went digging through git to see what might have changed in this respect.  I found [1] (Use curl_multi_fdset to select on curl fds instead of just sleeping) which seemed to describe the exact issue.  So I applied this to a local build and things seem to work much better, the clone happens as quickly as with git://

This is a small change but it makes a big difference in clone time over https, so I think it should be considered.

Will attach patch & packages I built for testing if interested

---
[root@cloud-server-01 test]# yum info git
Installed Packages
Name        : git
Arch        : x86_64
Version     : 1.7.1
Release     : 3.el6_4.1
Size        : 15 M
Repo        : installed
From repo   : base
---

[1] https://git.kernel.org/cgit/git/git.git/commit/?id=6f9dd67ffea3e86276a73e522ce1186a99bbe65d