diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -961,3 +961,24 @@ def rcpath():
         else:
             _rcpath = os_rcpath()
     return _rcpath
+
+def bytecount(nbytes):
+    '''return byte count formatted as readable string, with units'''
+
+    units = (
+        (100, 1<<30, _('%.0f GB')),
+        (10, 1<<30, _('%.1f GB')),
+        (1, 1<<30, _('%.2f GB')),
+        (100, 1<<20, _('%.0f MB')),
+        (10, 1<<20, _('%.1f MB')),
+        (1, 1<<20, _('%.2f MB')),
+        (100, 1<<10, _('%.0f KB')),
+        (10, 1<<10, _('%.1f KB')),
+        (1, 1<<10, _('%.2f KB')),
+        (1, 1, _('%.0f bytes')),
+        )
+
+    for multiplier, divisor, format in units:
+        if nbytes >= divisor * multiplier:
+            return format % (nbytes / float(divisor))
+    return units[-1][2] % nbytes