[PATCH v2] docs/system: clarify deprecation schedule

[Philippe Mathieu-Daudé]

On 9/15/20 5:07 PM, Stefan Hajnoczi wrote:
> The sentence explaining the deprecation schedule is ambiguous. Make it
> clear that a feature deprecated in the Nth release is guaranteed to
> remain available in the N+1th release. Removal can occur in the N+2nd
> release or later.
> 
> As an example of this in action, see commit
> 25956af3fe5dd0385ad8017bc768a6afe41e2a74 ("block: Finish deprecation of
> 'qemu-img convert -n -o'"). The feature was deprecated in QEMU 4.2.0. It
> was present in the 5.0.0 release and removed in the 5.1.0 release.
> 
> Suggested-by: Daniel P. Berrangé <berrange at redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd at redhat.com>

> ---
> v2:
>  * Use Dan's suggested wording [Daniel Berrange]
> ---
>  docs/system/deprecated.rst | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
> index 0cb8b01424..f2d5bd8ce1 100644
> --- a/docs/system/deprecated.rst
> +++ b/docs/system/deprecated.rst
> @@ -3,10 +3,11 @@ Deprecated features
>  
>  In general features are intended to be supported indefinitely once
>  introduced into QEMU. In the event that a feature needs to be removed,
> -it will be listed in this section. The feature will remain functional
> -for 2 releases prior to actual removal. Deprecated features may also
> -generate warnings on the console when QEMU starts up, or if activated
> -via a monitor command, however, this is not a mandatory requirement.
> +it will be listed in this section. The feature will remain functional for the
> +release in which it was deprecated and one further release. After these two
> +releases, the feature is liable to be removed. Deprecated features may also
> +generate warnings on the console when QEMU starts up, or if activated via a
> +monitor command, however, this is not a mandatory requirement.
>  
>  Prior to the 2.10.0 release there was no official policy on how
>  long features would be deprecated prior to their removal, nor
>