Errors are thrown when using platform=local

[reduckted]

How are you running Renovate?

Self-hosted Renovate

If you're self-hosting Renovate, tell us which platform (GitHub, GitLab, etc) and which version of Renovate.

platform=local; version=40.58.0

Please tell us more about your question or problem

I reported in #22264 (reply in thread) that using platform=local seemed like the best way to test changes to a Renovate config that is not on the default branch. Upon further inspection, the Renovate invocation actually stops in the "update" section because an error is thrown in syncGit.

renovate/lib/util/git/index.ts

Lines 404 to 407 in 2197818

	/* v8 ignore next 3 -- failsafe TODO: add test */
	if (GlobalConfig.get('platform') === 'local') {
	throw new Error('Cannot sync git when platform=local');
	}

Error: Cannot sync git when platform=local
    at syncGit (C:\Code\GitHub\renovatebot\renovate\lib\util\git\index.ts:2:12319)
    at getFile (C:\Codvatebot\renovate\lib\util\git\index.ts:2:27638)
    at getFileContent (C:\Code\GitHub\renovatebot\renovate\lib\workers\repository\update\branch\get-updated.ts:2:1
    at processBranch (C:\Code\GitHub\renovatebib\workers\repository\update\branch\index.ts:2:13810)
    at writeUpdates (C:\Code\GitHub\renovatebot\renovate\lib\workers\repository\process\write.ts:2:5491)

Because of this error, you are not able to test that the post-upgrade tasks run correctly. That part is really the missing piece to be able to test changes to a Renovate config before merging those changes into the default branch.

Logs (if relevant)

Logs

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