Fix update-geth.sh

ops/celo/update-geth.sh

@@ -3,15 +3,21 @@ set -eo pipefail
 
 branch="$1"
 if [ -z "$branch" ]; then
-  echo "No argument given. Please supply the ref in 'celo-org/op-geth' to be used "
+  echo "No argument given. Please supply the ref in 'celo-org/op-geth' to be used " >&2
   exit 1
 fi
 
 commit=$(git ls-remote https://github.com/celo-org/op-geth/ "$branch" | awk '{print $1}')
-if [ -z "$commit" ]; then exit 1; fi
+if [ -z "$commit" ]; then
+  echo "Could not find branch '$branch' in 'celo-org/op-geth'" >&2
+  exit 1
+fi
 
 go_version=$(go list -m "github.com/celo-org/op-geth@$commit")
-if [ -z "$go_version" ]; then exit 1; fi
+if [ -z "$go_version" ]; then
+  echo "Failed to generate go version string fork '$commit' in 'celo-org/op-geth'" >&2
+  exit 1
+fi
 
 sha256digest=$(gcloud --format=json artifacts files list \
   --project=blockchaintestsglobaltestnet \
@@ -20,10 +26,29 @@ sha256digest=$(gcloud --format=json artifacts files list \
   --package=op-geth \
   --limit=1 \
   --tag="$commit" | jq ".[0].name" | grep -oE 'sha256:([0-9a-f]{64})' | sed 's/^sha256://')
-if [ -z "$sha256digest" ]; then exit 1; fi
+if [ -z "$sha256digest" ]; then
+  echo "Failed to find sha256digest for op-geth docker image 'celo-org/op-geth'" >&2
+  exit 1
+fi
+
+# We need to escape the '@' otherwise '@sha256' is interpreted as a global
+# Symbol by perl.
+docker_search_string="(.*op-geth\@sha256:)(.*)"
+gomod_search_string="^(replace github.com/ethereum/go-ethereum .*=> )github.com/.*/op-geth v.*"
+
+# Check that the searches are each matching a single line
+if [ "$(perl -ne "m|$docker_search_string| && print" ops-bedrock/l2-op-geth.Dockerfile | wc -l)" != "1" ]; then
+  echo "Failed to find exactly one match for docker search string in ops-bedrock/l2-op-geth.Dockerfile" >&2
+  exit 1
+fi
+
+if [ "$(perl -ne "m|$gomod_search_string| && print" go.mod | wc -l)" != "1" ]; then
+  echo "Failed to find exactly one match for go mod search string in go.mod" >&2
+  exit 1
+fi
 
-perl -pi -e "s|(.*op-geth@sha256:)(.*)|\1$sha256digest|" ./ops-bedrock/l2-op-geth.Dockerfile
-perl -pi -e "s|^(replace github.com/ethereum/go-ethereum .* => )github.com/.*/op-geth v.*|\1$go_version|" go.mod
+perl -pi -e "s|$docker_search_string|\1$sha256digest|" ops-bedrock/l2-op-geth.Dockerfile
+perl -pi -e "s|$gomod_search_string|\1$go_version|" go.mod
 
 go_mod_error=$(go mod tidy >/dev/null)
 if [ -n "$go_mod_error" ]; then