[llvm-diff] Add colorful output to diff (#131012)

Adds colorful output when when possible to the diff. Adds a use to the
`--color` option llvm-diff has.

Author: Bertik23

llvm/tools/llvm-diff/lib/DiffConsumer.cpp

@@ -14,6 +14,8 @@
 #include "llvm/IR/Instructions.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/WithColor.h"
+#include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 
@@ -199,20 +201,23 @@ void DiffConsumer::logd(const DiffLogBuilder &Log) {
     switch (Log.getLineKind(I)) {
     case DC_match:
       out << "  ";
-      Log.getLeft(I)->print(dbgs()); dbgs() << '\n';
-      //printValue(Log.getLeft(I), true);
+      Log.getLeft(I)->print(dbgs());
+      dbgs() << '\n';
       break;
-    case DC_left:
-      out << "< ";
-      Log.getLeft(I)->print(dbgs()); dbgs() << '\n';
-      //printValue(Log.getLeft(I), true);
+    case DC_left: {
+      auto LeftColor = llvm::WithColor(out, raw_ostream::RED);
+      LeftColor << "< ";
+      Log.getLeft(I)->print(LeftColor);
+      LeftColor << '\n';
       break;
-    case DC_right:
-      out << "> ";
-      Log.getRight(I)->print(dbgs()); dbgs() << '\n';
-      //printValue(Log.getRight(I), false);
+    }
+    case DC_right: {
+      auto RightColor = llvm::WithColor(out, raw_ostream::GREEN);
+      RightColor << "> ";
+      Log.getRight(I)->print(RightColor);
+      RightColor << '\n';
       break;
     }
-    //out << "\n";
+    }
   }
 }