Skip dev_requirements/sdist install for changelog generation when using apistub

[msyyc]

Summary

The breaking check (used by changelog generation) unconditionally ran install_dev_reqs and a sdist create_package_and_install before invoking the detector. In --use-apistub mode these steps are unnecessary and can cause failures.

The apistub path in detect_breaking_changes.py builds the code report via static analysis (azpysdk apistub generates api.md, which is converted to a report) and never imports the target package. Therefore installing the package's dev_requirements.txt and building/installing the sdist is only needed for the legacy import-based path.

This also fixes a local failure during changelog generation (which always passes --use-apistub, see packaging_tools/package_utils.py): building wheels from local-source dev dependencies (azure-identity, azure-mgmt-resource) fails on Windows with [WinError 183] Cannot create a file when that file already exists due to stale in-source build/ artifacts. Skipping the install avoids the wheel build entirely and speeds up changelog generation.

Related: #48089

Changes

• azpysdk/breaking.py: guard install_dev_reqs and the sdist create_package_and_install behind not use_apistub. The jsondiff + breaking-change-checker install (install_into_venv) still runs in both modes, since the detector imports them.
• tests/test_breaking.py: new tests verifying that
  • with --use-apistub: install_dev_reqs and create_package_and_install are skipped, install_into_venv still runs, and the detector is invoked with --use-apistub;
  • default (import-based) path: both installs run and --use-apistub is not forwarded.

Validation

python -m pytest eng/tools/azure-sdk-tools/tests/test_breaking.py -v
# 2 passed

Files formatted with black -l 120.

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[Copilot]

Pull request overview

Skips unnecessary dependency and sdist installation when breaking-change detection uses static apistub analysis.

Changes:

• Guards package installation behind not use_apistub.
• Adds coverage for apistub and legacy paths.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
azpysdk/breaking.py	Skips unnecessary installs in apistub mode.
tests/test_breaking.py	Tests installation behavior for both modes.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.