Update logic for shell workdir

[jandubois]

Changes to the previous implementation are:

• If there are no volume mounts then there is no fallback to the host $HOME directory (because we know it isn't mounted, so no need to display an additional error).

• If the --workdir does not exist in the guest, we fallback to the host $PWD first before trying the host $HOME (because it is less surprising to stay in the current directory than to switch to one that is different from the requested one).

Testing with no mounts

No error message when --workdir is not specified, and only a single error message when the requested workdir does not exist:

$ limactl shell k3s bash
jan@lima-default:~$ pwd
/home/jan.linux
jan@lima-k3s:~$ exit
$ limactl shell --workdir /does-not-exist k3s bash
bash: line 1: cd: /does-not-exist: No such file or directory
jan@lima-default:~$ pwd
/home/jan.linux

Testing with a /tmp mount, but no home directory mount

Falls back to the host $PWD and $HOME. Uses guest $HOME when none of them exist:

$ limactl shell --workdir /does-not-exist default bash
bash: line 1: cd: /does-not-exist: No such file or directory
bash: line 1: cd: /Users/jan/suse/lima: No such file or directory
bash: line 1: cd: /Users/jan: No such file or directory
jan@lima-default:~$ pwd
/home/jan.linux

[AkihiroSuda]

What is this? Shouldn't this default to currentDir? (even when there is no mount)

[jandubois]

How can currentDir (from the host) work when there are no mounts? It is unlikely that a directory with the same name exists inside the VM, but even if it does, it will have different content.

I mean, potentially you could be in /tmp and then change to /tmp inside the guest, but when does that ever make sense? I think when you don't specify a --workdir with a VM that has no mounts, you should end up in the home directory inside the VM.

So false is just something that returns a non-zero exit code, because when there are mounts, the command becomes:

false || cd currentDir || cd homeDir

We must have something on the left side of the || that fails (but doesn't show an error on stderr), so the cd currentDir will be tried next.

[AkihiroSuda]

Thanks for explanation. After merging this, I'll add logrus.Debug for better readability