ADDing files that may be missing

[dreyks]

I have files on host that may not always be present on build time, e.g. caches. Those are tar'ed for performance, that's why I use a separate ADD argument
I know that such technique is generally discouraged as one that may produce non-deterministic builds but this is still doable with docker

ADD . caches* ./

this way in case caches.tar is present on host - its content gets untarred and placed into the image. If it's not present - nothing bad happens

when using buildkit i'm getting #19 75.18 panic: failed to copy /src-1/caches* to app/: no matches found: /src-1/caches*

[tonistiigi]

Thanks for the report. Need to make sure FileOp #396 can do this weird error handling where one suboperation is allowed to fail.

On the other hand, you are right that this is discouraged and undocumented behavior. It might be even considered a bug of the old implementation. Eg. if you compare it to regular cp behavior it is BuildKit that is working correctly in this case and not the old builder.

[tonistiigi]

Also, note that you can use RUN --mount for more control of accessing your data now (filters etc.). And we also have --mount=type=cache that you might actually need if you want to persist some files to speed up builds.

[dreyks]

yeah just stumbled upon that doc. thanks a lot

once again I fully understand that this may not be the intended behaviour. In such case maybe it'd be enough to just add a line to the doc

[dreyks]

also I think it's the * that allows docker not to fail