fix: .commit-info.json info/exclude entry resolves against the runner cwd, not the checkout (PR #17 does not take effect) #36

Found while triaging Eyevinn/wasm-runner#19 (the parity port of web-runner#51).

scripts/docker-entrypoint.sh (PR #17, 4aca5a6) resolves the exclude file with excl="$(git -C "$repo_dir" rev-parse --git-path info/exclude)" (around :140). git prints that path relative to the -C directory (.git/info/exclude), not to the script's cwd. write_commit_info /usercontent is called at ~:182 while the cwd is /runner (Dockerfile WORKDIR /runner, first cd /usercontent at ~:189), so the append never reaches /usercontent/.git/info/exclude and git -C /usercontent status --porcelain still lists .commit-info.json.

Reproduction (git 2.39.5, real function extracted from the entrypoint, called from a cwd that is not the repo): the porcelain still prints ?? .commit-info.json and the append fails with .git/info/exclude: No such file or directory. With an absolute path (case "$excl" in /*) ;; *) excl="$repo_dir/$excl" ;; esac) the porcelain is empty and a second call adds no second line. Live pod state was not read.

Acceptance criteria:

• git -C /usercontent status --porcelain does not list .commit-info.json after the entrypoint ran from /runner.
• A regression test in tests/ extracts the real write_commit_info, calls it from a cwd that is not the repo, and asserts an empty git status --porcelain and one exclude line after two calls; it fails against the current block.
• No file is added to the user's tracked tree and no commit is created.

Related: python-runner#16 (closed), web-runner#51, wasm-runner#19.

Related: Eyevinn/wasm-runner#19