fix(upgrade): look for version string in logs bottom up (#8926)

For in place upgrade, the container remains the same and the logs have
the version string twice, one for the old container and one for the new
container. We want the version string in the logs for the new container.
Hence, we look for the string in the logs bottom up by using
strings.LastIndex instead of strings.Index.

dgraphtest/image.go

@@ -23,6 +23,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 
 	"github.com/pkg/errors"
 )
@@ -137,7 +138,7 @@ func getHash(ref string) (string, error) {
 	if out, err := cmd.CombinedOutput(); err != nil {
 		return "", errors.Wrapf(err, "error while running rev-parse on [%v]\noutput:%v", ref, string(out))
 	} else {
-		return string(out), nil
+		return strings.TrimSpace(string(out)), nil
 	}
 }
 

dgraphtest/local_cluster.go

@@ -796,7 +796,11 @@ func (c *LocalCluster) checkDgraphVersion(containerID string) error {
 	if err != nil {
 		return errors.Wrapf(err, "error during checkDgraphVersion for container [%v]", containerID)
 	}
-	index := strings.Index(contLogs, "Commit SHA-1     : ")
+
+	// During in-place upgrade, container remains same but logs have version string twice
+	// once for old version, once for new. Want new version string. Look bottom-up using
+	// LastIndex to get latest version's string.
+	index := strings.LastIndex(contLogs, "Commit SHA-1     : ")
 	running := strings.Fields(contLogs[index : index+70])[3] // 70 is arbitrary
 	chash, err := getHash(c.GetVersion())
 	if err != nil {
@@ -807,7 +811,7 @@ func (c *LocalCluster) checkDgraphVersion(containerID string) error {
 		return errors.Wrapf(err, "error while getting hash for %v", running)
 	}
 	if chash != rhash {
-		return errors.Errorf("found different dgraph version than expected [%v]", c.GetVersion())
+		return errors.Errorf("found different dgraph version [%v] than expected [%v]", rhash, chash)
 	}
 	return nil
 }