Make show command more resilient when resolving references

Currently the show command can print internal object, which requires a local environment.
This goes against the sql migration expectations that there is no environment. This change
only makes the situation less bad. Splitting out the admin operations into another command
is the right approach.

go/cmd/dolt/commands/show.go

@@ -127,26 +127,40 @@ func (cmd ShowCmd) Exec(ctx context.Context, commandStr string, args []string, d
 		defer closeFunc()
 	}
 
+	resolvedRefs := make([]string, 0, len(opts.specRefs))
+	for _, specRef := range opts.specRefs {
+		if !hashRegex.MatchString(specRef) && !strings.EqualFold(specRef, "HEAD") {
+			// Call "dolt_hashof" to resolve the ref to a hash. the --no-pretty flag gets around the commit requirement, but
+			// requires the full object name so it will match the hashRegex and never his this code block.
+			h, err2 := getHashOf(queryist, sqlCtx, specRef)
+			if err2 != nil {
+				cli.PrintErrln("error: failed to resolve ref to commit: %s ", specRef)
+				return 1
+			}
+			resolvedRefs = append(resolvedRefs, h)
+		} else {
+			resolvedRefs = append(resolvedRefs, specRef)
+		}
+	}
+	if len(resolvedRefs) == 0 {
+		resolvedRefs = []string{"HEAD"}
+	}
+
 	// There are two response formats:
 	//  - "pretty", which shows commits in a human-readable fashion
 	//  - "raw", which shows the underlying SerialMessage
 	// All responses should be in the same format.
 	// The pretty format is preferred unless the --no-pretty flag is provided.
 	// But only commits are supported in the "pretty" format.
 	// Thus, if the --no-pretty flag is not set, then we require that either all the references are commits, or none of them are.
-
-	isDEnvRequired := false
-
 	if !opts.pretty {
-		isDEnvRequired = true
-	}
-	for _, specRef := range opts.specRefs {
-		if !hashRegex.MatchString(specRef) && !strings.EqualFold(specRef, "HEAD") {
-			isDEnvRequired = true
+		if dEnv == nil {
+			// Logic below requires a non-nil dEnv when --no-pretty is set.
+			// TODO: remove all usage of dEnv entirely from this command.
+			cli.PrintErrln("`\\show` is not fully supported in the SQL shell.")
+			return 1
 		}
-	}
 
-	if isDEnvRequired {
 		// use dEnv instead of the SQL engine
 		_, ok := queryist.(*engine.SqlEngine)
 		if !ok {
@@ -160,12 +174,7 @@ func (cmd ShowCmd) Exec(ctx context.Context, commandStr string, args []string, d
 		}
 	}
 
-	specRefs := opts.specRefs
-	if len(specRefs) == 0 {
-		specRefs = []string{"HEAD"}
-	}
-
-	for _, specRef := range specRefs {
+	for _, specRef := range resolvedRefs {
 		// If --no-pretty was supplied, always display the raw contents of the referenced object.
 		if !opts.pretty {
 			err := printRawValue(ctx, dEnv, specRef)
@@ -176,20 +185,25 @@ func (cmd ShowCmd) Exec(ctx context.Context, commandStr string, args []string, d
 		}
 
 		// If the argument is a commit, display it in the "pretty" format.
-		// But if it's a hash, we don't know whether it's a commit until we query the engine.
-		commitInfo, err := getCommitSpecPretty(queryist, sqlCtx, opts, specRef)
+		// But if it's a hash, we don't know whether it's a commit until we query the engine. If a non-commit was specified
+		// by the user, we are forced to display the raw contents of the object - which required a dEnv
+		commitInfo, err := getCommitSpecPretty(queryist, sqlCtx, specRef)
 		if commitInfo == nil {
 			// Hash is not a commit
 			_, ok := queryist.(*engine.SqlEngine)
 			if !ok {
 				cli.PrintErrln("`dolt show (NON_COMMIT_HASH)` only supported in local mode.")
 				return 1
 			}
-
-			if !opts.pretty && !dEnv.DoltDB.Format().UsesFlatbuffers() {
+			if dEnv == nil {
+				cli.PrintErrln("`dolt show (NON_COMMIT_HASH)` requires a local environment. Not intended to common use.")
+				return 1
+			}
+			if !dEnv.DoltDB.Format().UsesFlatbuffers() {
 				cli.PrintErrln("`dolt show (NON_COMMIT_HASH)` is not supported when using old LD_1 storage format.")
 				return 1
 			}
+
 			value, err := getValueFromRefSpec(ctx, dEnv, specRef)
 			if err != nil {
 				err = fmt.Errorf("error resolving spec ref '%s': %w", specRef, err)
@@ -211,6 +225,8 @@ func (cmd ShowCmd) Exec(ctx context.Context, commandStr string, args []string, d
 	return 0
 }
 
+// printRawValue prints the raw value of the object referenced by specRef. This function works directly on storage, and
+// requires a non-nil dEnv.
 func printRawValue(ctx context.Context, dEnv *env.DoltEnv, specRef string) error {
 	value, err := getValueFromRefSpec(ctx, dEnv, specRef)
 	if err != nil {
@@ -220,6 +236,8 @@ func printRawValue(ctx context.Context, dEnv *env.DoltEnv, specRef string) error
 	return nil
 }
 
+// getValueFromRefSpec returns the value of the object referenced by specRef. This
+// function works directly on storage, and requires a non-nil dEnv.
 func getValueFromRefSpec(ctx context.Context, dEnv *env.DoltEnv, specRef string) (types.Value, error) {
 	var refHash hash.Hash
 	var err error
@@ -303,7 +321,7 @@ func parseHashString(hashStr string) (hash.Hash, error) {
 	return parsedHash, nil
 }
 
-func getCommitSpecPretty(queryist cli.Queryist, sqlCtx *sql.Context, opts *showOpts, commitRef string) (commit *CommitInfo, err error) {
+func getCommitSpecPretty(queryist cli.Queryist, sqlCtx *sql.Context, commitRef string) (commit *CommitInfo, err error) {
 	if strings.HasPrefix(commitRef, "#") {
 		commitRef = strings.TrimPrefix(commitRef, "#")
 	}