pull: Always request detached metadata for commits

Always request detached metadata for commit objects, even if we already
have the commit object.  This ensures we fetch any post facto detached
metadata updates such as new GPG signatures.

https://bugzilla.gnome.org/748220

tests/test-commit-sign.sh

@@ -51,7 +51,6 @@ mkdir baz/another/
 echo x > baz/another/y
 ${CMD_PREFIX} ostree --repo=${test_tmpdir}/ostree-srv/gnomerepo commit -b main -s "The rest" --gpg-sign=$keyid --gpg-homedir=${SRCDIR}/gpghome
 cd ..
-rm -rf gnomerepo-files
 
 cd ${test_tmpdir}
 mkdir ${test_tmpdir}/httpd
@@ -106,3 +105,23 @@ ${CMD_PREFIX} ostree --repo=repo init
 ${CMD_PREFIX} ostree --repo=repo remote add --set=gpg-verify=false origin $(cat httpd-address)/ostree/gnomerepo
 ${CMD_PREFIX} ostree --repo=repo pull origin main
 rm repo -rf
+
+# Add an unsigned commit to the repo, then pull, then sign the commit,
+# then pull again.  Make sure we get the expected number of signatures
+# each time.
+cd ${test_tmpdir}/ostree-srv/gnomerepo-files
+echo secret > signme
+${CMD_PREFIX} ostree --repo=${test_tmpdir}/ostree-srv/gnomerepo commit -b main -s "Don't forget to sign me!"
+cd ${test_tmpdir}
+mkdir repo
+${CMD_PREFIX} ostree --repo=repo init
+${CMD_PREFIX} ostree --repo=repo remote add --set=gpg-verify=false origin $(cat httpd-address)/ostree/gnomerepo
+${CMD_PREFIX} ostree --repo=repo pull origin main
+if ${CMD_PREFIX} ostree --repo=repo show main | grep -o 'Found [[:digit:]] signature'; then
+  assert_not_reached
+fi
+${CMD_PREFIX} ostree --repo=${test_tmpdir}/ostree-srv/gnomerepo gpg-sign --gpg-homedir=${SRCDIR}/gpghome main $keyid
+${CMD_PREFIX} ostree --repo=repo pull origin main
+${CMD_PREFIX} ostree --repo=repo show main | grep -o 'Found [[:digit:]] signature' > show
+assert_file_has_content show 'Found 1 signature'
+rm -rf repo gnomerepo-files