schema: add support for tmpfs.mode in mount definition

[milas]

⚠️ Draft until compose-spec/compose-go#325 is merged & tagged

What I did
Add support for tmpfs.mode to set permissions on tmpfs mounts

Related issue

• Volumes of type tmpfs lacks support for the mode parameter #9873
• schema: add tmpfs.mode field compose-spec/compose-go#325

(not mandatory) A picture of a cute animal, if possible in relation to what you did

[thaJeztah]

we may have to look if mode is fully functional as well; I recall this ticket, and I don't think we dug to the end of that one yet (at least I haven't found time to dig into it myself);

• tmpfs-mode has no effect on nested mounts moby/moby#40881

[milas]

we may have to look if mode is fully functional as well

Thanks for sharing that! I think it's still fine to add here unless we're planning on deprecating tmpfs support entirely - once/if the upstream bug is fixed, nested permissions should start just working in Compose after upgrading engine. For now, this will at least give parity in that permissions on unnested tmpfs mounts are now supported

[thaJeztah]

Thanks for sharing that! I think it's still fine to add here unless we're planning on deprecating tmpfs support entirely - once/if the upstream bug is fixed, nested permissions should start just working in Compose after upgrading engine. For now, this will at least give parity in that permissions on unnested tmpfs mounts are now supported

Yup, change looks okay to me; mostly recalled that there was an issue around this option, and thought I'd mention it to set the expectations right 😄. Trying / testing /digging on that linked issue is always welcome as well (I created that ticket to have it at least written down somewhere as a reminder)

@milas looks like this needs a rebase now (conflict in go.sum)

[milas]

Yeah, it's in draft as it needs the updated schema code from compose-go so will be fixing that when I remove my replaces