Keep the upstream's version

The safe way out of the same state after a local change, made before a merge or pull recorded the rewritten commit: splice the rewritten upstream in again, and redo the local change on top of it. The upstream's history stays as rewritten, which matters if the rewrite removed something, like a secret.

Output

setup.bash builds this state:

$ build_scenario scenario_upstream_rewritten_equal_tree

$ echo "local change" >>vendor/a/file.txt && git commit -q -a -m "local change" && git splice status
On branch main

  !! unrelated history  vendor/a  see 'git splice merge vendor/a' for options

Save the local change as a patch, with paths inside the folder:

$ git diff --relative=vendor/a HEAD~1 -- vendor/a >../local-change.patch

Remove the folder, and splice the rewritten upstream in again:

$ git rm -r -q -- vendor/a && git commit -q -m "remove vendor/a" && git splice clone -- "$UPSTREAM" vendor/a
===  vendor/a: fetching $UPSTREAM
ok   vendor/a: cloned bc05937 from main

Redo the local change, and push it:

$ git apply --directory=vendor/a ../local-change.patch && git commit -q -a -m "local change" && git splice push vendor/a
ok   vendor/a: pushed 5c7d4e1 to main

The upstream's history is still the rewritten one:

$ git -C "$UPSTREAM" log --format=%s main
local change
release, history rewritten

Output​

Output