t9005-workspace-commit-push: setup pushes to `main` on a `master` repo

[mizchi]

Corrected. The original version listed two failures. Test 3 was an artifact of the environment I triaged in and is retracted below; the setup failure is genuine.

Summary

t/t9005-workspace-commit-push.sh fails 1 of 7 where init.defaultBranch is unset and git defaults to master.

not ok 1 - setup: create upstream bare repository and working clone
# passed: 6   failed: 1

The failing assertion

	mkdir upstream.git &&
	(cd upstream.git && git init --bare) &&
	git clone upstream.git work &&
	(cd work &&
	 git config user.email "test@example.com" &&
	 git config user.name "Test User" &&
	 echo "v1" > app.txt &&
	 git add app.txt &&
	 git commit -m "initial" &&
	 git push origin main)

The clone's branch is master, so git push origin main fails and the setup step reports failure.

Suggested fix

Pin the branch at git init — -b main, or git symbolic-ref HEAD refs/heads/main for git older than 2.28.

Same class as #191 (fixed in #192), #193 and #194.

Retraction: test 3

I originally flagged not ok 3 - implicit commit creates workspace commit with transaction trailer alongside this, and speculated it might be a second defect in implicit translation.

It is not. It was the same environment artifact described in #194: the container exports GIT_CONFIG_*, which makes should_delegate_to_real_git (modules/bit/cmd/bit/main.mbt:1044) hand the command to the real git binary before workspace_translate_implicit_command can run. With those variables unset only the setup failure above remains.