[Feature Request] Show diff summary between branches (files changed, insertions and deletions)

[assisjrt]

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Description:

Fork currently has no native way to display a summary of the total differences between two branches — such as the number of files changed and the total lines added or removed.

This is equivalent to running:

git diff origin/main...origin/my-branch --stat

Or GitHub's compare view (/compare/main...my-branch), which shows something like:

42 files changed, 1,823 insertions(+), 540 deletions(-)

What would be useful:

• A summary panel or tooltip when comparing two branches
• Display of total files changed, lines added, and lines removed

Context:
This information is very helpful before opening a Pull Request, giving a high-level overview of the impact of changes without having to leave the app or run terminal commands.