Add dolt_preview_merge_conflicts table function

go/libraries/doltcore/merge/merge_prolly_rows.go

@@ -78,7 +78,7 @@ func mergeProllyTable(
 	if err != nil {
 		return nil, nil, err
 	}
-	valueMerger := NewValueMerger(mergedSch, tm.leftSch, tm.rightSch, tm.ancSch, leftRows.Pool(), tm.ns)
+	valueMerger := tm.GetNewValueMerger(mergedSch, leftRows)
 
 	if !valueMerger.leftMapping.IsIdentityMapping() {
 		mergeInfo.LeftNeedsRewrite = true

go/libraries/doltcore/merge/merge_rows.go

@@ -112,6 +112,10 @@ func (tm TableMerger) AncRows(ctx context.Context) (prolly.Map, error) {
 	return rowsFromTable(ctx, tm.ancTbl)
 }
 
+func (tm TableMerger) InvolvesRootObjects() bool {
+	return tm.leftRootObj != nil || tm.rightRootObj != nil || tm.ancRootObj != nil
+}
+
 func (tm TableMerger) tableHashes(ctx context.Context) (left, right, anc hash.Hash, err error) {
 	if tm.leftTbl != nil {
 		if left, err = tm.leftTbl.HashOf(); err != nil {
@@ -238,8 +242,7 @@ func (rm *RootMerger) MergeTable(
 
 	var tbl *doltdb.Table
 	var rootObj doltdb.RootObject
-	involvesRootObjects := tm.leftRootObj != nil || tm.rightRootObj != nil || tm.ancRootObj != nil
-	if !involvesRootObjects {
+	if !tm.InvolvesRootObjects() {
 		if types.IsFormat_DOLT(tm.vrw.Format()) {
 			tbl, stats, err = mergeProllyTable(ctx, tm, mergeSch, mergeInfo, diffInfo)
 		} else {

go/libraries/doltcore/sqle/dtablefunctions/dolt_diff.go

@@ -315,7 +315,7 @@ func loadCommitStrings(ctx *sql.Context, fromRef, toRef, dotRef interface{}, db
 func interfaceToString(r interface{}) (string, error) {
 	str, ok := r.(string)
 	if !ok {
-		return "", fmt.Errorf("received '%v' when expecting commit hash string", str)
+		return "", fmt.Errorf("received '%v' when expecting commit hash string", r)
 	}
 	return str, nil
 }