Your bug report

#21262: 25.0.50; Diff-mode gets confused about its narrowing if hunk source not found

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 21262@debbugs.gnu.org.

-- 
21262: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21262
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