`extract_changed_files` parses `diff --git a/<old> b/<new>` headers.
A host `diff.mnemonicprefix=true` or `diff.noprefix=true` rewrote them
(`c/ w/`, or none), so every tracked change vanished from `changed_files`
and the two evidence git-diff tests failed on such hosts. Both capture
paths now pass `--src-prefix=a/ --dst-prefix=b/`, which override both
config keys. Regression test sets each key in the temp repo.
Claude-Session: https://claude.ai/code/session_01RUqV8HVGXcAETyYbZ2tPQ4
雷电芽衣
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