[AIR-3026] qs: GetRootFolder is called in many places. Call it once

[host6]

AIR-3026 qs: GetRootFolder is called in many places. Call it once
https://untill.atlassian.net/browse/AIR-3026

[augmentcode]

🤖 Augment PR Summary

Summary: This PR reduces redundant repo-root discovery when setting up git hooks, avoiding repeated git rev-parse --show-toplevel subprocess calls.

Changes:

• Refactors `gitcmds/hook.go` helpers to accept a precomputed rootDir instead of calling GetRootFolder() multiple times.
• Updates call chains in local/global pre-commit hook setup and large-file-hook maintenance to resolve the root once per operation.
• Simplifies local hook-path computation by passing the resolved root directory down.
• Extends status parsing to handle the MD porcelain state alongside deletions.
• Adds archived uspec documentation describing the motivation and implementation plan.

Technical Notes: Net effect is fewer GetRootFolder()/git invocations in common hook flows while keeping behavior otherwise consistent.

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[augmentcode]

Review completed. 1 suggestions posted.

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