Address stacks and envs by path

[jamesroutley]

Implementation

We currently build stacks and environments with the syntax:

sceptre <action>-stack env stack
sceptre <action>-env env

This proposal would change the addressing to:

sceptre <action> path/to/stack.yaml
sceptre <action> --recursive path/to/env/

Pros

• By supplying file paths, we get native tab completion (only tested on zsh on macOS)

Cons

[theseanything]

Pro this! But not sure about the --recursive flag.

[mitom]

Instead of --recursive could we have just:

sceptre <action> path/to/env/

As in passing in a directory would be the same as launch-env and passing in a file would be the same as launch-stack?

[theseanything]

Yeah that would be ideal. But we need to put some sort of protection around doing actions to a whole environment. It would be too easy for a user to accidentally create or update stacks unintentionally. CloudFormation slip-ups can be costly :(

[jamesroutley]

@seanrankine what about it are you not sure about?

[theseanything]

its in an awkward position and the word recursive is long... Just means its not super easy to switch between a stack or env command in the terminal.

[jamesroutley]

oh yeah I think we'd do a -r as well.

[theseanything]

Yup but still not a huge fan of it sitting in between the command and path. It'd be nice to just tack it on the end

[mitom]

I'd rather have it in front, -r is not too bad and flags generally come in front of positional arguments, not after.

Also, to avoid potentially harmful/accidental actions you could add a simple verification
You are about to update the entire <env> envrionment, do you want to continue? [Y|n]. It would make it easy to switch between commands (no other arguments need to change) and it would make it clear what is going to happen. For CI tools a -y flag could assume yes.

[theseanything]

I like the verification step way of doing it and the safety. Thoughts @jamesroutley? Also would we want to put .yaml at the end of a stack? I'd prefer to omit it.

[jamesroutley]

I've opened an issue about adding verification to the delete commands #61. Should we add one for other commands as well? Maybe for "dangerous" commands like update?

I put the .yaml for a couple of reasons:

1. Sceptre fundamentally deals with files. Each stack maps onto a single file. I think it's beneficial to emphasise this by getting users to supply a path to a file.
2. Using an actual file path gives you tab-completion. This completes to /path/stack.yaml, so if we didn't have the .yaml users could tab in the filename but would have to delete those five chars
3. It makes the yaml vs yml thing ( Allow .yml as well as .yaml #67 ) a bit more explicit and removes some ambiguity about which one we use.

[theseanything]

#278