fix: handle binary diff without extended header

[yeonjuan]

fixes #22

[codecov-commenter]

Codecov Report

Merging #23 (2844672) into main (62d8908) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #23   +/-   ##
=======================================
  Coverage   98.45%   98.45%           
=======================================
  Files           4        4           
  Lines         194      194           
  Branches       59       59           
=======================================
  Hits          191      191           
  Misses          2        2           
  Partials        1        1           

Flag	Coverage Δ
unittest	98.45% <100.00%> (ø)

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Files Changed	Coverage Δ
src/parse-git-diff.ts	98.25% <100.00%> (ø)