diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -528,6 +528,16 @@
         labels.append(b'base')
     return _imerge(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels)
 
+@internaltool(
+    b'merge3-lie-about-conflicts',
+    fullmerge,
+    b'',
+    precheck=_mergecheck,
+)
+def _imerge3alwaysgood(*args, **kwargs):
+    b1, junk, b2 = _imerge3(*args, **kwargs)
+    return b1, False, b2
+
 
 def _imergeauto(
     repo,