fix: handle multiple diff lines

[yeonjuan]

fixes #31

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.46%. Comparing base (d2a5a5e) to head (ca33de4).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #32 +/- ## ========================================== + Coverage 98.45% 98.46% +0.01% ========================================== Files 4 4 Lines 194 196 +2 Branches 59 60 +1 ========================================== + Hits 191 193 +2 Misses 2 2 Partials 1 1 ``` | [Flag](https://app.codecov.io/gh/yeonjuan/parse-git-diff/pull/32/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=YeonJuan) | Coverage Δ | | |---|---|---| | [unittest](https://app.codecov.io/gh/yeonjuan/parse-git-diff/pull/32/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=YeonJuan) | `98.46% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=YeonJuan#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files with missing lines](https://app.codecov.io/gh/yeonjuan/parse-git-diff/pull/32?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=YeonJuan) | Coverage Δ | | |---|---|---| | [src/parse-git-diff.ts](https://app.codecov.io/gh/yeonjuan/parse-git-diff/pull/32?src=pr&el=tree&filepath=src%2Fparse-git-diff.ts&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=YeonJuan#diff-c3JjL3BhcnNlLWdpdC1kaWZmLnRz) | `98.27% <100.00%> (+0.02%)` | :arrow_up: |