[FFmpeg-devel] Patch question

Mats Peterson matsp888 at yahoo.com
Tue Dec 15 18:00:34 CET 2015

On 12/15/2015 05:49 PM, Moritz Barsnick wrote:
> Hi Mats,
> On Tue, Dec 15, 2015 at 16:58:41 +0100, Mats Peterson wrote:
>> Sorry if this may sound idiotic, but if I provide a unified patch for a
>> file that is newer/different from the one I have here, it won't work, right?
> "It depends." ;-)
> By the way, git handles this kind of stuff nicely.
> It may or may not work. Obviously, if the file hasn't changed upstream,
> your patch will still apply.
> a) Best case: The files haven't changed upstream, your diff still
>     applies.
> b) Good case: Upstream changed only unrelated parts of those file, your
>     diff applies, perhaps with an offset (i.e. shifted in line numbers).
> b2) Almost as good: The unrelated changes are close to your changes, so
>     you get a so-called fuzz.
> c) Bad case: Related parts were changed. Your diff won't apply, you
>     have to reintegrate your changes, perhaps even differently.
> d) Worse case: Your patch applies, but affected methods were
>     incompatibly changed. This leads to build or runtime errors, or
>     broken functionality.
> It's always a good idea to check upstream changes to see whether they
> affect your patch. Most likely, a) or b) applies, but you don't know
> until you've checked. :-)
> Moritz
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Thanks for the enlightening answer, Moritz. Now I don't possess an 
enormous amount of Git experience, but I guess it's best to get the 
latest version from Git before providing any new patches. It makes life 
easier for the potential testers, of course.


Mats Peterson

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