FWIW I doubt Git is any better at this than Mercurial: <https://github.com/python/cpython/blame/master/Lib/test/test_string.py#L190>

Git can automatically pick up file renames and copies when analysing the history, but has no special metadata for this. I understand Mercurial is the opposite (has metadata, but at least by default does not pick up copies and renames from the history). Perhaps that is what Benjamin was thinking of. I understand Git will only pick up movements of the majority of a file, not parts of files (unless something has changed recently).

Perhaps Serhiy can clarify, but I imagine he was proposing something like this (which I have not tested):

A. Start at revision A
B. Remove test_string and rename test_pep292 in its place, giving revision B
C. Merge revisions A and B, and manually merge the contents of the two test_string versions, giving the final revision