Windows: '--portable' command-line directive for binary-relative paths

[britkig]

Inspired by feature request #1539 for more-secure file‑based (quick) tunnel configurations, I would like to propose a --portable switch for Windows builds.

When cloudflared is launched via the the Service Control Manager (SCM), the SCM sets the initial working directory to %SystemRoot%\System32. This prevents the use of drive‑relative rooted paths (e.g. \srv\cloudflare\...), which would otherwise allow configurations to survive drive‑letter changes — a common scenario after OS reinstalls or storage layout changes.

The proposed --portable switch could trigger cloudflared to set its active/working directory, at the earliest possible timing, to where the executable itself resides. This behaviour could be on a opt‑in basis and would mitigate breaking existing setups.

While the path to the executable must remain absolute, allowing drive‑relative paths everywhere else reduces the risk of breakages when drive letters change.

Example 1

Config

"X:\bin\cloudflared.exe" --portable --config="/srv/cloudflare/tunnel.yml" tunnel run 

Resolves to X:\srv\cloudflare\tunnel.yml.

Credentials

tunnel: ...
credentials-file: /srv/cloudflare/tunnel.json
ingress:
  - service: http://127.0.0.1

Resolves to X:\srv\cloudflare\tunnel.json.

Example 2

Config

"C:\Program Files\Cloudflared\cloudflared.exe" --portable --config="tunnel.yml" tunnel run 

Resolves to C:\Program Files\Cloudflared\tunnel.yml.

Credentials

tunnel: ...
credentials-file: tunnel.json
ingress:
  - service: http://127.0.0.1

Resolves to C:\Program Files\Cloudflared\tunnel.json.