feat(BREV-2866): open shell in expected container working directory

[nisolanki1209]

Problem

When launching a custom container, brev shell did not take the container’s WORKDIR into account. It opened a standard shell session, which defaults to the root user’s home directory, instead of the container’s WORKDIR.

As a result, users were placed in /root rather than the container’s intended WORKDIR.

Solution

Updated the runSSH function to detect and respect the container’s WORKDIR when launching brev shell.

• Detect the container WORKDIR by reading /proc/1/cwd (PID 1 working directory).
• Fallback to pwd if /proc/1/cwd is unavailable.
• Change into the resolved directory before starting the shell.
• Print a warning if the directory is not found, but still launch the shell to avoid blocking access to the container.
• Use ${SHELL} with /bin/sh as a fallback for minimal containers.

[Copilot]

Pull request overview

This PR updates the brev shell command to respect the container's WORKDIR when opening an interactive shell session in a custom container. Previously, users were placed in the default SSH login directory (/root) regardless of the container's intended working directory.

Changes:

• The runSSH function signature is updated to accept a host bool parameter, and the call site is updated accordingly.
• When host=false (the container path), the SSH command now reads /proc/1/cwd via readlink (with pwd as a fallback) to determine the container's working directory, then cds into it before executing the shell.
• The host=true path retains the original simple ssh command behavior without modifications.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The shell is launched via exec ${SHELL:-/bin/sh} without the login flag (-l). This means the shell doesn't source login initialization files (such as /etc/profile, ~/.profile, or ~/.bash_profile). As a result, environment variables such as PATH and other shell customizations set in those files may not be available, which could break user tools and workflows. The original ssh alias command would spawn a login shell by default. To preserve login shell behavior, use exec -l ${SHELL:-/bin/sh} (POSIX) or exec ${SHELL:-/bin/sh} -l.

Suggested change

	cmd = fmt.Sprintf("%s && ssh -t %s 'DIR=$(readlink -f /proc/1/cwd 2>/dev/null || pwd); cd \"$DIR\" || echo \"Warning: Could not access container directory\" >&2; exec ${SHELL:-/bin/sh}'", sshAgentEval, sshAlias)
	cmd = fmt.Sprintf("%s && ssh -t %s 'DIR=$(readlink -f /proc/1/cwd 2>/dev/null || pwd); cd \"$DIR\" || echo \"Warning: Could not access container directory\" >&2; exec -l ${SHELL:-/bin/sh}'", sshAgentEval, sshAlias)