Update generated projects without a Git history to lean on

Bringing a generated project or component forward when its template changes means computing a three-way merge: what changed in the template since you last generated, layered onto whatever you've customized locally. That merge needs a base — a snapshot of what the template looked like at the point you started from — and the obvious place to find one is the project's own commit history. But not every generated project has intact history to read: it might not be a Git repository at all, its history might have been squashed or rewritten by a different tool, or it might simply be old enough that the base commit no longer exists on any reachable branch. Any of those and --update had nothing to work with.

The Problem

atmos init --update and atmos scaffold generate --update read the merge base directly from the target directory's own Git history, at whichever ref was pinned when the project was first generated. That works well when the target is a Git repository with intact history — but it also means --update fails outright the moment it isn't: no Git repo, a rewritten or squashed history, or a base commit that's since been garbage-collected all leave the merge with no base to compare against.

It has a second, quieter cost even when history is intact: because the pinned base ref never advances, the gap between "what the template looked like at that pin" and "what it looks like now" only grows with every successive update — so does the conflict surface.

The Fix

--update-strategy chooses where that merge base comes from, independently of --merge-strategy (how a conflict resolves) and --merge-driver (which merge algorithm runs):

• tracked (default, unchanged) — the merge base is read from the target's own Git history, exactly as before.
• rendered — the merge base is a fresh, pristine re-render of the template itself, at the ref that produced what's currently on disk, using that generation's own recorded answers. There's no Git read involved at all, so it works whether or not the target is (or still is) a Git repository — and because it re-renders from the last update rather than the original pin, the base never drifts further than one update cycle behind.

rendered needs a scaffold.yaml-driven template, since it relies on the answers Atmos already records in .atmos/scaffold.yaml from the prior generation to reproduce that render faithfully. A plain --set-only template has no such record to replay, so rendered isn't available for those yet — use tracked there.

How to Use It

# Everyday updates: tracked (the default) keeps reading from Git history.
atmos scaffold generate my-template ./my-project --update

# No Git history to lean on, or you just want the merge base to stay current
# with the last update instead of the original pin.
atmos scaffold generate my-template ./my-project --update --update-strategy=rendered
atmos init --update --update-strategy=rendered

Get Involved

See the atmos scaffold generate and atmos init docs for the full flag reference. Have feedback on this feature? Open an issue or join the conversation in the Cloud Posse community Slack.