Workspace checkout reports an existing default branch as missing on repositories with many branches #9195

Summary

The workspace checkout script reports the workspace default branch as missing when the repository has a large number of branches, even though the branch exists. Implement then fails with:

The workspace default branch "develop" does not exist in https://bitbucket.org/<workspace>/<repo>.git. The repository's default branch is "master". Update it in Workspace settings → Repository.

The message happens for every branch, including the repository's own default branch (master above). Planning shows the same problem as a warning and falls back to the remote default branch.

Cause

WorkspaceCheckoutScript() in pkg/components/runner/workspace_agent_resources.go runs with set -euo pipefail and checks the branch like this:

heads="$(git ls-remote --heads "${REPO_URL}")" || exit 1
if [ -n "$requested_branch" ] && printf '%s\n' "$heads" | awk '{print $2}' | grep -Fxq "refs/heads/${requested_branch}"; then

grep -q exits on the first match. When the ls-remote output is larger than the pipe buffer, printf or awk is still writing and gets SIGPIPE. Under pipefail, the pipeline then reports failure, so a branch that matched is treated as missing.

Reproduction

set -euo pipefail
heads="$(printf '%040d\trefs/heads/develop\n' 0; for i in $(seq 1 5000); do printf '%040d\trefs/heads/feature/branch-%d-with-a-longish-name\n' 0 $i; done)"
printf '%s\n' "$heads" | awk '{print $2}' | grep -Fxq refs/heads/develop && echo found || echo "not found"
# prints: not found

Fix

Let grep read all of its input:

printf '%s\n' "$heads" | awk '{print $2}' | grep -Fx "refs/heads/${requested_branch}" >/dev/null

I have this fix locally, with a regression test in workspace_checkout_test.go. The test creates a bare repo with 3,000 branches and checks that the requested branch is checked out. I can open a PR.

Environment

• Bitbucket repository with several hundred branches
• Local development setup (make dev.up, Docker Fleet Manager runner)