tests/payload-link: Just test a single duplicate object

We were previously assuming that the host content had duplicates,
which...hopefully it doesn't!  We shouldn't rely on that.

Also this test is slow in production and flaky.  Let's just test
a single duplicate object.

Closes: #1509
Approved by: jlebon

tests/installed/itest-payload-link.sh

@@ -31,9 +31,16 @@ prepare_tmpdir /var/tmp
 trap _tmpdir_cleanup EXIT
 ostree --repo=repo init --mode=archive
 echo -e '[archive]\nzlib-level=1\n' >> repo/config
-host_nonremoteref=$(echo ${host_refspec} | sed 's,[^:]*:,,')
-ostree --repo=repo pull-local /ostree/repo ${host_commit}
-ostree --repo=repo refs ${host_commit} --create=${host_nonremoteref}
+
+mkdir content
+cd content
+dd if=/dev/urandom of=bigobject bs=4k count=2560
+cp --reflink=auto bigobject bigobject2
+# Different metadata, same content
+chown bin:bin bigobject2
+cd ..
+ostree --repo=repo commit -b dupobjects --consume --selinux-policy=/ --tree=dir=content
+ostree --repo=repo summary -u
 
 run_tmp_webserver $(pwd)/repo
 
@@ -53,23 +60,24 @@ if ! blkdev=$(losetup --find --show $(pwd)/testblk.img); then
     exit 0
 fi
 
+# This filesystem must support reflinks
 mkfs.xfs -m reflink=1 ${blkdev}
 
 mount ${blkdev} mnt
 cd mnt
 
-# Test that coreutils will do reflink
+# Test that reflink is really there (not just --reflink=auto)
 touch a
 cp --reflink a b
 mkdir repo
 ostree --repo=repo init
 ostree config --repo=repo set core.payload-link-threshold 0
 ostree --repo=repo remote add origin --set=gpg-verify=false ${origin}
-ostree --repo=repo pull --disable-static-deltas origin ${host_nonremoteref}
+ostree --repo=repo pull --disable-static-deltas origin dupobjects
 find repo -type l -name '*.payload-link' >payload-links.txt
-assert_not_streq "$(wc -l < payload-links.txt)" "0"
+assert_streq "$(wc -l < payload-links.txt)" "1"
 
-# Disable logging for inner loop, otherwise it'd be enormous
+# Disable logging for inner loop
 set +x
 cat payload-links.txt | while read i; do
     payload_checksum=$(basename $(dirname $i))$(basename $i .payload-link)