censor: document the censor.policy option (issue6909)

Censor is not marked as experimental and should be documented

I am not doing this on stable because the help markup change it is using seems
more suitable for default.

hgext/censor.py

@@ -24,10 +24,11 simply fail when asked to produce censor
 function in a meaningful way. Such commands only tolerate censored file
 As having a censored version in a checkout is impractical. The current head
 revisions of the repository are checked. If the revision to be censored is in
-any of them the command will abort.
+any of them the command will abort. You can configure this behavior using the
+following option:
 
-A few informative commands such as ``hg grep`` will unconditionally
-ignore censored data and merely report that it was encountered.
+    `censor.policy`
+        :config-doc:`censor.policy`
 """
 
 

mercurial/configitems.toml

@@ -65,7 +65,13 default = ""
 section = "censor"
 name = "policy"
 default = "abort"
-experimental = true
+documentation="""Control how to react when accessing censored content.
+Accepted value: "abort", "ignore". Defaults to abort.
+
+A few informative commands such as ``hg grep`` will unconditionally ignore
+censored data and merely report that it was encountered.
+"""
+
 
 [[items]]
 section = "chgserver"

mercurial/helptext/config.txt

@@ -418,6 +418,12 Supported arguments:
 If no suitable authentication entry is found, the user is prompted
 for credentials as usual if required by the remote.
 
+``censor``
+----------
+
+``policy``
+    :config-doc:`censor.policy`
+
 ``cmdserver``
 -------------