Diff

Fetch a diff based on the input scope.

Scope detection

$ARGUMENTS determines the scope. Auto-detect the type:

Input	Diff command
A PR number (e.g., 123)	gh pr diff 123
A commit SHA (7-40 hex chars)	git diff {sha}~1 {sha}
A commit range (a..b)	git diff a b
A branch name	git diff {base}...{branch} (detect base: gh pr view --json baseRefName -q .baseRefName 2>/dev/null, fall back to main)
staged or pending	git diff --staged
current or empty	git diff HEAD

If empty and the working tree is clean, fall back to the current branch vs main.

Output

Write the diff to a temp file and read it with the Read tool — diffs frequently exceed inline output limits.

If reviewing a PR, also read the PR description. If reviewing a commit, also read the commit messages.

Provide a report of the diffs:

Title: <Summary of PR title and commit messages> Description: <Summary of PR description and commit descriptions> Size: <size (XS|S|M|L|XL|XXL)> Diffs: <path to diff file>

Size guidelines:

Size	Lines	Files	Review complexity
XS	< 50	1-2	Trivial: minor typos, documentation, or config tweaks
S	50-200	3-5	Ideal: single bug fix or small, focused feature
M	200-400	6-10	Standard: complete feature or logical refactor
L	400-1k	11-20	Warning: high cognitive load, reviewers may start skimming
XL	1k-2k	20+	Critical: likely needs to be split into smaller, independent PRs
XXL	2k+	50+	Dangerous: defect detection drops significantly

Use whichever dimension gives the larger size (e.g., 3 files but 500 lines = L).