help: document rewrite.backup-bundle option

hgext/histedit.py

@@ -1680,7 +1680,6 b' def _histedit(ui, repo, state, *freeargs'
     fm.startitem()
     goal = _getgoal(opts)
     revs = opts.get('rev', [])
-    # experimental config: rewrite.backup-bundle
     nobackup = not ui.configbool('rewrite', 'backup-bundle')
     rules = opts.get('commands', '')
     state.keep = opts.get('keep', False)

mercurial/help/config.txt

@@ -1812,6 +1812,9 b' Alias definitions for revsets. See :hg:`'
 ``rewrite``
 -----------
 
+``backup-bundle``
+    Whether to save stripped changesets to a bundle file. (default: True)
+
 ``update-timestamp``
     If true, updates the date and time of the changeset to current. It is only
     applicable for hg amend in current version.