fix(precommit): handle filenames with spaces in Commit.from_merge

[gg-jonathangriffe]

Context

When using git merge with a file which has a space in its name, the command fails with the error :

• ValueError: too many values to unpack (expected 4)

What has been done

Since the path is at the end of the parsed line (whose other components do not include spaces), we can simple add maxsplit=3 as an argument to split.

Validation

• Make a repo
• Create a file with a space in its name in a first branch
• In another branch, create the same file with a different content
• In a branch run git merge <other_branch>
• Resolve the conflict and run git merge --continue
  If there is no error, it means the bug is fixed.

PR check list

• As much as possible, the changes include tests (unit and/or functional)
• If the changes affect the end user (new feature, behavior change, bug fix) then the PR has a changelog entry (see doc/dev/getting-started.md). If the changes do not affect the end user, then the skip-changelog label has been added to the PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.91%. Comparing base (118ca6d) to head (c97a92b).
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #992      +/-   ##
==========================================
+ Coverage   91.58%   91.91%   +0.32%     
==========================================
  Files         180      181       +1     
  Lines        7605     7593      -12     
==========================================
+ Hits         6965     6979      +14     
+ Misses        640      614      -26     

Flag	Coverage Δ
unittests	91.91% <100.00%> (+0.32%)	⬆️

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[agateau-gg]

Super minor remark. I approved nevertheless, feel free to merge when it's fixed.