fix(git): keep special-character paths from git name-only listings

[r3wretrhy]

fix(git): keep special-character paths from git name-only listings

git diff --name-only and git ls-files --others C-quote paths that contain " or non-ASCII when core.quotepath is on. fetchChangedFiles then split those quoted lines, so yarn workspaces list --since attributed the change to the root workspace instead of the real one.

Pass -z and split on NUL so each path stays one entry.

Fixes #6804

What's the problem this PR addresses?

When a changed file has special characters in the name (for example "), git diff --name-only wraps the path in C-quotes. fetchChangedFiles split on newlines and treated that quoted string as the path, so tryWorkspaceByFilePath missed the workspace and yarn workspaces list --since reported the root instead.

Closes #6804

How did you fix it?

Use git diff -z --name-only and git ls-files -z --others --exclude-standard, then split the stdout on NUL. Same listing, no quoting.

Testing

• yarn test:unit packages/plugin-git/tests/gitUtils.test.ts — 91 passed, including a temp-repo regression that stages and leaves untracked files whose names git would C-quote.
• Added --since keeps workspaces whose changed files have special characters in the name next to the existing --since list tests.

Checklist

• I have read the Contributing Guide.
• I have set the packages that need to be released for my changes to be effective.
• I will check that all automated PR checks pass before the PR gets reviewed.