shrink-revlog: add --dry-run option

contrib/shrink-revlog.py

@@ -189,14 +189,19 b' def shrink(ui, repo, **opts):'
             if os.path.exists(tmpdatafn):
                 os.unlink(tmpdatafn)
             raise
+        if not opts.get('dry_run'):
         # Racy since both files cannot be renamed atomically
         util.os_link(indexfn, oldindexfn)
         util.os_link(datafn, olddatafn)
         util.rename(tmpindexfn, indexfn)
         util.rename(tmpdatafn, datafn)
+        else:
+            os.unlink(tmpindexfn)
+            os.unlink(tmpdatafn)
     finally:
         lock.release()
 
+    if not opts.get('dry_run'):
     ui.write('note: old revlog saved in:\n'
           '  %s\n'
           '  %s\n'
@@ -207,7 +212,9 b' def shrink(ui, repo, **opts):'
 
 cmdtable = {
     'shrink': (shrink,
-               [('', 'revlog', '', 'index (.i) file of the revlog to shrink')],
+               [('', 'revlog', '', 'index (.i) file of the revlog to shrink'),
+                ('n', 'dry-run', None, 'do not shrink, simulate only'),
+                ],
                'hg shrink [--revlog PATH]')
 }