Add recipe annotation to prevent cd-ing to justfile

[casey]

Proposed along with a few other features in #761, moving into its own issue to track separately.

It might be nice to have a recipe annotation that makes just use the invocation directory as the current working directory for that recipe, like so:

#[no_cd]
foo:
  pwd # will print invocation directory, not justfile directory

[tcassaert]

Until this is implemented, you can add

#!/usr/bin/env bash
cd -

which will take you back to the directory where you executed the just command.

[casey]

I can't get this to work:

foo:
  #!/usr/bin/env bash
  pwd
  cd -
  pwd

$ just foo
/Users/rodarmor/tmp/cd
/var/folders/b5/q2c4mxk534v6kwdtx2mpw91m0000gn/T/justF2cWhz/foo: line 4: cd: OLDPWD not set
/Users/rodarmor/tmp/cd

[tcassaert]

Hmmm, I can only get it to work when my Justfile is located in $HOME/Justfile. Didn't pay attention to that...

[casey]

We have recipe attributes now, so this was very simple to implement. It's available on master if you want to give it a shot!