In brief
git apply --check checks whether a patch can apply without writing its changes. This separates preliminary compatibility from modifying files.
Useful to know
git apply --check checks whether a patch can apply without writing its changes. This separates preliminary compatibility from modifying files. [1]
A successful check does not prove the new logic is correct. Actual application still needs review and relevant tests. Plain git apply also does not automatically create a commit documenting the finished change.
Sources
For further detail and to check the information: