fix(bootstrap): auto-disable constraints and extend e2e test coverage

[rd4398]

Two related fixes for --multiple-versions flag:

1. Auto-disable constraints with --multiple-versions

   • When --multiple-versions flag is enabled, automatically set skip_constraints=True because constraints.txt cannot handle multiple versions of the same package
   • Log informative message: "automatically disabling constraints generation (incompatible with --multiple-versions)"

2. Extend e2e test to verify dependency chain handling

   • Use generous constraint range (flit-core>=3.9,<3.12) instead of pinning to single version
   • Verify that multiple versions of flit-core are built (not just tomli), confirming --multiple-versions works for entire chain
   • Check for at least 2 flit-core versions (test found 3)
   • Remove || true since constraints are now auto-disabled

The e2e test now validates that --multiple-versions bootstraps multiple versions of both top-level packages AND their dependencies, providing better test coverage.

Fixes: #1044
Fixes: #1045

[coderabbitai]

📝 Walkthrough

Walkthrough

The changes implement automatic constraint disabling for the --multiple-versions mode and extend the e2e test to verify multiple build backend versions are exercised. The bootstrap command now forces skip_constraints=True when --multiple-versions is enabled, eliminating constraint generation failures. The test script updates the generated constraints from a pinned version to a version range (flit-core>=3.9,<3.12), removes error suppression that previously masked constraint failures, and adds post-bootstrap verification that at least 2 distinct flit_core-3.*.whl wheels were actually built.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main changes: auto-disabling constraints with --multiple-versions and extending e2e test coverage.
Description check	✅ Passed	The description provides clear details on both fixes, including the rationale for auto-disabling constraints and extending test coverage with specific examples.
Linked Issues check	✅ Passed	The PR fully addresses both issues: constraints are auto-disabled when --multiple-versions is enabled [#1044], and e2e test uses generous constraint ranges to verify multiple dependency versions build [#1045].
Out of Scope Changes check	✅ Passed	All changes are directly scoped to the linked issues: bootstrap.py adds auto-disable logic for constraints, and the e2e test is extended to validate multiple versions of dependencies.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@e2e/test_bootstrap_multiple_versions.sh`:
- Line 13: The trap currently expands $constraints_file when the trap is
registered rather than at exit, and won't handle paths with spaces; change the
trap registration for rm -f $constraints_file to use single quotes around the
command and quote the variable inside (i.e., trap 'rm -f "$constraints_file"'
EXIT) so the variable is expanded at runtime and paths with spaces are handled
safely; update the trap line that references constraints_file accordingly.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 45560f03-d9fd-44c4-a6d5-fe08dd291471

📥 Commits

Reviewing files that changed from the base of the PR and between b8f4441 and c4cea97.

📒 Files selected for processing (2)

• e2e/test_bootstrap_multiple_versions.sh
• src/fromager/commands/bootstrap.py

[jskladan]

FWIW, LGTM @rd4398