diff -r e06d1a779eb6 -r 3b56395404a1 mercurial/revlog.py
--- a/mercurial/revlog.py	Tue May 30 17:43:59 2023 +0100
+++ b/mercurial/revlog.py	Wed May 31 10:37:55 2023 +0100
@@ -290,6 +290,16 @@
 
     _flagserrorclass = error.RevlogError
 
+    @staticmethod
+    def is_inline_index(header_bytes):
+        header = INDEX_HEADER.unpack(header_bytes)[0]
+
+        _format_flags = header & ~0xFFFF
+        _format_version = header & 0xFFFF
+
+        features = FEATURES_BY_VERSION[_format_version]
+        return features[b'inline'](_format_flags)
+
     def __init__(
         self,
         opener,