PR comparison widget shows stale diff counter when comparing same branch

Description

The branch comparison / PR creation widget in the Claude Code input area shows a stale diff counter (+20 -2744) even when:

• Both sides of the comparison are the same branch (main ← main)
• The working tree is clean (git status shows no changes)
• Local and remote are in sync (git diff origin/main..main is empty)
• There are no other branches in the repository

The counter does not clear after committing, pushing, or restarting the Claude Code session.

Steps to reproduce

1. Have a repo with a single branch (main), fully pushed, clean working tree
2. Open Claude Code in the project directory
3. Observe the main ← main comparison widget showing a non-zero diff counter

Expected behaviour

When comparing the same branch to itself with no uncommitted changes, the counter should show +0 -0 or the widget should be hidden entirely.

Possible cause

The repository was recently renamed from master to main. The counter may be cached from a previous comparison between the two branches before master was deleted. Alternatively, untracked files (even gitignored ones) may have been included in the diff calculation.

Environment

• Claude Code CLI (Opus 4.6)
• Windows 11, Git for Windows
• Single-branch repo, no PRs, no CI/CD