Merge branch 'jt/fast-export-copy-modify-fix' into maint

"git fast-export" with -M/-C option issued "copy" instruction on a
path that is simultaneously modified, which was incorrect.

* jt/fast-export-copy-modify-fix:
  fast-export: do not copy from modified file

diff --cc builtin/fast-export.c
Simple merge

diff --cc t/t9350-fast-export.sh
Simple merge