diff --git a/hgext/extdiff.py b/hgext/extdiff.py
--- a/hgext/extdiff.py
+++ b/hgext/extdiff.py
@@ -101,6 +101,7 @@
     error,
     filemerge,
     formatter,
+    logcmdutil,
     pycompat,
     registrar,
     scmutil,
@@ -568,7 +569,7 @@
         ctx1b = repo[nullrev]
         ctx2 = scmutil.revsingle(repo, to_rev, None)
     else:
-        ctx1a, ctx2 = scmutil.revpair(repo, revs)
+        ctx1a, ctx2 = logcmdutil.revpair(repo, revs)
         if not revs:
             ctx1b = repo[None].p2()
         else:
diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -2610,7 +2610,7 @@
         ctx2 = scmutil.revsingle(repo, to_rev, None)
     else:
         repo = scmutil.unhidehashlikerevs(repo, revs, b'nowarn')
-        ctx1, ctx2 = scmutil.revpair(repo, revs)
+        ctx1, ctx2 = logcmdutil.revpair(repo, revs)
 
     if reverse:
         ctxleft = ctx2
@@ -6909,7 +6909,7 @@
         ctx1 = ctx2.p1()
     else:
         repo = scmutil.unhidehashlikerevs(repo, revs, b'nowarn')
-        ctx1, ctx2 = scmutil.revpair(repo, revs)
+        ctx1, ctx2 = logcmdutil.revpair(repo, revs)
 
     forcerelativevalue = None
     if ui.hasconfig(b'commands', b'status.relative'):
diff --git a/mercurial/logcmdutil.py b/mercurial/logcmdutil.py
--- a/mercurial/logcmdutil.py
+++ b/mercurial/logcmdutil.py
@@ -912,6 +912,18 @@
     return None
 
 
+def revpair(repo, revs):
+    """Resolves user-provided revset(s) into two revisions.
+
+    This just wraps the lower-level scmutil.revpair() in order to raise an
+    exception indicating user error.
+    """
+    try:
+        return scmutil.revpair(repo, revs)
+    except error.RepoLookupError as e:
+        raise error.InputError(e.args[0], hint=e.hint)
+
+
 def revrange(repo, specs, localalias=None):
     """Resolves user-provided revset(s).
 
diff --git a/tests/autodiff.py b/tests/autodiff.py
--- a/tests/autodiff.py
+++ b/tests/autodiff.py
@@ -4,6 +4,7 @@
 
 from mercurial import (
     error,
+    logcmdutil,
     patch,
     pycompat,
     registrar,
@@ -49,7 +50,7 @@
     else:
         raise error.Abort(b'--git must be yes, no or auto')
 
-    ctx1, ctx2 = scmutil.revpair(repo, [])
+    ctx1, ctx2 = logcmdutil.revpair(repo, [])
     m = scmutil.match(ctx2, pats, opts)
     it = patch.diff(
         repo,