Merge branch 'jc/fake-ancestor-with-non-blobs' into maint

Rebasing the history of superproject with change in the submodule has been broken since v1.7.12. * jc/fake-ancestor-with-non-blobs: apply: diagnose incomplete submodule object name better apply: simplify build_fake_ancestor() git-am: record full index line in the patch used while rebasing