[Repo Assist] refactor(rust-guard): extract short_sha helper to fix 5-site duplication and 7-vs-8 inconsistency

[github-actions]

🤖 This PR was created by Repo Assist, an automated AI assistant.

Closes #7308

Root Cause

The SHA truncation idiom (if sha.len() > 8 { &sha[..8] } else { sha }) was copy-pasted across 5 locations in 4 files, and silently diverged in length:

• 4 sites used 8 characters (helpers.rs ×2, tool_rules.rs, response_items.rs)
• 1 site used 7 characters (response_paths.rs) — the Git-canonical short SHA length

This means commit descriptions and log messages were inconsistent depending on the code path that produced them.

Fix

Added a single canonical helper in labels/helpers.rs:

/// Truncate a SHA to the standard 7-character short form used by GitHub's UI
/// and `git log --abbrev`. Returns the full string unchanged when it is already
/// shorter than 7 characters.
#[inline]
pub(crate) fn short_sha(sha: &str) -> &str {
    &sha[..sha.len().min(7)]
}

All 5 inline expressions replaced with short_sha(sha) / short_sha(&commit_sha). The 4 "8-char" sites now produce the same 7-char prefix as response_paths.rs, matching GitHub's UI and git log --abbrev.

Changes

File	Change
labels/helpers.rs	Added short_sha() helper + 3 unit tests; replaced 2 inline expressions
labels/tool_rules.rs	Added short_sha to imports; replaced 1 inline expression
labels/response_items.rs	Replaced 1 inline expression (uses helpers::* glob)
labels/response_paths.rs	Replaced 1 inline expression (uses helpers::* glob)

Test Status

✅ Rust guard tests: All 461 tests pass, including 3 new short_sha unit tests:

• short_sha_truncates_full_sha_to_7
• short_sha_leaves_short_shas_intact
• short_sha_handles_empty_string

⚠️ Go tests: Build failed due to infrastructure — proxy.golang.org is blocked in this environment and Go module cache is incomplete. This is a pre-existing constraint unrelated to these Rust-only changes. The Go code is unchanged.

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[Copilot]

Pull request overview

This PR refactors the Rust guard labeling code to centralize SHA truncation into a single helper, eliminating duplicated inline truncation logic and making short-SHA formatting consistent across commit-related descriptions/logs.

Changes:

• Added short_sha(&str) -> &str helper in labels/helpers.rs with unit tests.
• Replaced 5 inline SHA truncation expressions across labeling modules with short_sha(...).
• Standardized all short SHA outputs to 7 characters (matching Git/GitHub UI conventions).

Show a summary per file

File	Description
guards/github-guard/rust-guard/src/labels/helpers.rs	Adds the short_sha helper and unit tests; replaces two in-file truncation sites.
guards/github-guard/rust-guard/src/labels/tool_rules.rs	Imports and uses short_sha for commit description formatting.
guards/github-guard/rust-guard/src/labels/response_items.rs	Uses short_sha when labeling commit items in legacy (cloning) response labeling.
guards/github-guard/rust-guard/src/labels/response_paths.rs	Uses short_sha when labeling commit paths in path-based response labeling.

Copilot's findings

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• Files reviewed: 4/4 changed files
• Comments generated: 1

[lpcox]

@copilot fix this failing ci check https://github.com/github/gh-aw-mcpg/actions/runs/27287036012/job/80597223427?pr=7316

[Copilot]

@copilot fix this failing ci check https://github.com/github/gh-aw-mcpg/actions/runs/27287036012/job/80597223427?pr=7316

The smoke-copilot-pr failure was a transient 401 authentication error when the CI tried to dispatch the smoke-copilot.lock.yml workflow — it's not related to any code changes in this PR. The same job succeeded in the previous run attempt on this branch. I've re-queued the failed job to re-run.

[lpcox]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved in commit 053eb87. There was one conflict in helpers.rs — main had added 5 new extract_repo_scope_with_query_fallback tests right after the spot where this PR inserted the short_sha tests. Both sets are now present and all 466 Rust guard tests pass.