bin/docker-dev-shell: Teach DOCKER env variable

[bb010g]

DOCKER=podman bin/docker-dev-shell now works.

LOCAL_CODE_DIR eases running bin/docker-dev-shell with MSYS2 Bash.

[jeffwidman]

👋 Thanks for this and sorry for the delay reviewing. It would be nice to support podman etc.

However, I see three unrelated changes here:

1. $DOCKER
2. switch echo -> printf
3. $LOCAL_CODE_DIR

Since they are unrelated, can you break them out into separate PR's? It's just easier to discuss them that way, as I had a couple of questions about items 2 and 3.

Note to myself: for 3, see also https://github.com/dependabot/dependabot-core/pull/4056/files#diff-6fe5c8444caeeec4882a7d5173b9497a104b0f419f1d7c26b4fc848aa7e40d66R76

[bb010g]

echo "$msg" to printf '%s\n' "$msg" shouldn't result in different functionality under Bash (echo's behavior with regard to escape sequences isn't portable), except that when $msg starts with - it'll print as expected and not try to be parsed as an option. It's good shell script hygiene. (See Bash Pitfall #14.)

The introduction of $LOCAL_CODE_DIR to override $(pwd) is because MSYS2's Bash (which is an easy way to run this without WSL2) prints a path on pwd that Podman's native Windows build can't deal with. I'm guessing this is similar to what that other pull request ran into. I don't know of a way to solve this without giving the user the ability to directly override this path.

[jeffwidman]

Thanks, I'm actually aware of most of ☝️... but they're still unrelated changes, so at the very least they should be separate commits, and by that time it's easier to review/discuss as separate PR's.

Additionally, from time to time we have to revert commits/PRs for various unexpected reasons, and it's a lot nicer if we can keep that revert scoped to a single logical change so that we don't have a side effect of rolling back other changes that are still fine to keep.

To be clear, I'm 👍 on all these changes so far as I can tell from a quick glance at this PR... so should be straightforward, but they do need to be broken up.

[jeffwidman]

@bb010g Did you see my comment ☝️ ?

Any interest in moving this forward by splitting it up?