lib/pull: Add timestamp-check-from-rev

The way `timestamp-check` works might be too restrictive in some
situations. Essentially, we need to support the case where users want to
pull an older commit than the current tip, but while still guaranteeing
that it is newer than some even older commit.

This will be used in Fedora CoreOS. For more information see:
https://github.com/coreos/rpm-ostree/pull/2094
https://github.com/coreos/fedora-coreos-tracker/issues/481

tests/pull-test.sh

@@ -318,7 +318,7 @@ ${CMD_PREFIX} ostree --repo=parentpullrepo rev-parse origin:main > main.txt
 assert_file_has_content main.txt ${rev}
 echo "ok pull specific commit"
 
-# test pull -T
+# test pull -T and --timestamp-check-from-rev
 cd ${test_tmpdir}
 repo_init --no-sign-verify
 ${CMD_PREFIX} ostree --repo=repo pull origin main
@@ -347,6 +347,28 @@ assert_file_has_content err.txt "Upgrade.*is chronologically older"
 assert_streq ${newrev} "$(${CMD_PREFIX} ostree --repo=repo rev-parse main)"
 # But we can pull it without timestamp checking
 ${CMD_PREFIX} ostree --repo=repo pull origin main
+# Now test --timestamp-check-from-rev. First, add two new commits with distinct
+# but newer timestamps.
+oldrev=${newrev2}
+middlerev=$(${CMD_PREFIX} ostree --repo=ostree-srv/gnomerepo commit ${COMMIT_ARGS} -b main --tree=ref=main)
+sleep 1
+latestrev=$(${CMD_PREFIX} ostree --repo=ostree-srv/gnomerepo commit ${COMMIT_ARGS} -b main --tree=ref=main)
+${CMD_PREFIX} ostree --repo=ostree-srv/gnomerepo summary -u
+# OK, let's pull the latest now.
+${CMD_PREFIX} ostree --repo=repo pull -T origin main
+assert_streq ${latestrev} "$(${CMD_PREFIX} ostree --repo=repo rev-parse main)"
+# Check we can't pull the middle commit by overrides with ts checking on
+if ${CMD_PREFIX} ostree --repo=repo pull -T origin main@${middlerev} 2>err.txt; then
+    fatal "pulled older commit override with timestamp checking enabled?"
+fi
+assert_file_has_content err.txt "Upgrade.*is chronologically older"
+# Check we can't pull an older commit by override if it's newer than --timestamp-check-from-rev
+if ${CMD_PREFIX} ostree --repo=repo pull --timestamp-check-from-rev=${latestrev} origin main@${middlerev} 2>err.txt; then
+    fatal "pulled older commit override with timestamp checking enabled?"
+fi
+assert_file_has_content err.txt "Upgrade.*is chronologically older"
+# But we can pull it with --timestamp-check-from-rev when starting from the oldrev
+${CMD_PREFIX} ostree --repo=repo pull --timestamp-check-from-rev=${oldrev} origin main@${middlerev}
 echo "ok pull timestamp checking"
 
 cd ${test_tmpdir}