The GitHub provider now reads headRefOid and baseRefOid in one GraphQL query,
returns `stale` when the head moved, and reads the patch from
`compare/<baseRefOid>...<headSha>` instead of bracketing `gh pr diff` with two
head reads. Both ends are fixed commits. The compare read lives in the internal
`readComparison` helper so commit-range diffs can reuse it.
For every open and merged pull request measured, the compare patch is
byte-identical to `gh pr diff`. Unlike the pull request diff, it returns diffs
over 300 files, so such a pull request now shows its complete diff; only output
over `maxOutputBytes` or GitHub's HTTP 406 / `too_large` refusal is
`too-large`. The read passes `--allow-escape-sequences`, which gh 2.97 and
newer require to print patches whose files contain terminal escape sequences.
Yichen Jiang
7dc864a931