GitHub push rejected: shallow clone cannot push history (missing object / index-pack failed)

Problem

Pushing a branch from a --depth 1 clone to a new empty repository fails because the upstream history objects are missing.

Error (redacted / normalized)

error: remote unpack failed: index-pack failed
fatal: the remote end hung up unexpectedly

Applies when

git shallow clone (depth 1) of a large upstream repo; pushing to a new remote

Root cause

A shallow clone lacks parent commits; the remote refuses a history whose objects it cannot reconstruct.

Fix

1. Either git fetch --unshallow origin (downloads full history), or
2. Create an orphan branch with a single commit: git checkout --orphan main && git add -A && git commit -m 'Initial import' && git push -u newremote main.

How to verify

git push completes and the remote shows the branch.

What did not work

git push --force; increasing http.postBuffer.

Risks

Orphan branch drops upstream history (fine for forks you do not intend to sync via git).