Auto-format selection

Before I send this snippet for review, make the selected lines easy to approve: format them, align closing braces and indent nested blocks, break overly long expressions into shorter lines, and flag any changed local variable names or removed comments that might alter intent.

I formatted a selection but unrelated lines outside my selection were altered. I fear global formatting rules or trailing whitespace handling applied to the whole file. I cannot tell why the formatter widened its scope. What likely caused this and how should I safely restore only the intended selection formatting?

I try to format just blocks during iterative editing, but each time more of the file gets changed and my commits become hard to review. What practice or editor setting should I adopt so selective formatting stays local and I maintain small, reviewable commits?