Over NFS, git clone fails:

$ git clone URL directory
Cloning into 'directory'...
fatal: Unable to create temporary file
'.../.git/objects/pack/tmp_pack_XXXXXX': Permission denied
fatal: fetch-pack: invalid index-pack output

325727      0.000030 openat(AT_FDCWD,
"/home/rover/intranet-src/.git/objects/pack/tmp_pack_jIbpEU",
O_RDWR|O_CREAT|O_EXC
L, 0444) = -1 EACCES (Permission denied)

The problem seems to be the O_RDWR + 0444, that fails on NFS, but not on
ext4 or tmpfs.

Confirmed with this code, it returns same error:

openat(AT_FDCWD, "testfile", O_RDWR|O_CREAT|O_EXCL, 0444) = -1 EACCES
(Permission denied)

#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>

int
main() {
        int fd=open("testfile", O_RDWR|O_CREAT|O_EXCL, 0444);
        printf("errno=%d\n", errno);
        unlink("testfile");
        close(fd);
}