Clarify where the RUN command runs from

[julien-lecomte]

File: engine/reference/commandline/exec.md

This page should mention that the run command runs from the last WORKDIR specified.

Also, chained/quoted shell does not work:
docker run --rm toto "cd /foobar && touch me" fails...

[shubheksha]

I'll take this up!

[JimGalasyn]

@shubheksha how's your progress on this? We'll need to return this to the unclaimed pool for the hackathon by tomorrow, if we don't see movement. Thanks!

[shubheksha]

I'll fix this!

[JimGalasyn]

Cool, thanks!

[shubheksha]

This needs to be fixed in https://github.com/moby/moby I think?

[mdlinville]

Yes, @shubheksha :) In the docs/reference/commandline/ directory.

[jmaitrehenry]

Trying to fix it in moby/moby#32831