getFileDiffsWithBasehead(): use CODE_SCANNING_REPOSITORY if present #4629

Job	Run time
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.15.5)	1m 29s
Go: tracing with autobuilder step (macos-latest, stable-v2.16.6)	3m 58s
Go: tracing with autobuilder step (macos-latest, stable-v2.15.5)	4m 0s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.16.6)	1m 24s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.17.6)	1m 26s
Go: tracing with autobuilder step (macos-latest, stable-v2.17.6)	3m 55s
Go: tracing with autobuilder step (macos-latest, stable-v2.18.4)	4m 16s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.18.4)	1m 45s
Go: tracing with autobuilder step (ubuntu-latest, default)	1m 21s
Go: tracing with autobuilder step (macos-latest, stable-v2.19.4)	5m 36s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.19.4)	1m 26s
Go: tracing with autobuilder step (ubuntu-latest, linked)	1m 32s
Go: tracing with autobuilder step (macos-latest, default)	3m 33s
Go: tracing with autobuilder step (macos-latest, linked)	5m 9s
Go: tracing with autobuilder step (macos-latest, nightly-latest)	4m 21s
Go: tracing with autobuilder step (ubuntu-latest, nightly-latest)	1m 18s
	46m 29s

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