docs: add description to commands and index page

docs/content/commands/rclone_config_update.md

@@ -1,6 +1,7 @@
 ---
-date: 2020-02-10T15:06:43Z
+date: 2020-05-18T10:38:09+01:00
 title: "rclone config update"
+description: "Update options in an existing remote."
 slug: rclone_config_update
 url: /commands/rclone_config_update/
 # autogenerated - DO NOT EDIT, instead edit the source code in cmd/config/update/ and as part of making a release run "make commanddocs"
@@ -21,7 +22,17 @@ you would do:
     rclone config update myremote swift env_auth true
 
 If any of the parameters passed is a password field, then rclone will
-automatically obscure them before putting them in the config file.
+automatically obscure them if they aren't already obscured before
+putting them in the config file.
+
+**NB** If the password parameter is 22 characters or longer and
+consists only of base64 characters then rclone can get confused about
+whether the password is already obscured or not and put unobscured
+passwords into the config file. If you want to be 100% certain that
+the passwords get obscured then use the "--obscure" flag, or if you
+are 100% certain you are already passing obscured passwords then use
+"--no-obscure".  You can also set osbscured passwords using the
+"rclone config password" command.
 
 If the remote uses OAuth the token will be updated, if you don't
 require this add an extra parameter thus:
@@ -36,7 +47,9 @@ rclone config update <name> [<key> <value>]+ [flags]
 ### Options
 
 ```
-  -h, --help   help for update
+  -h, --help         help for update
+      --no-obscure   Force any passwords not to be obscured.
+      --obscure      Force any passwords to be obscured.
 ```
 
 See the [global flags page](/flags/) for global options not listed here.