What happens when a single file changes in a Git repository?
When one file changes, its blob hash changes, causing its parent tree hash to update, which propagates to the root tree hash and finally the commit hash. Unchanged sibling files and directories keep their hashes identical, so Git's status check skips them entirely—only changed paths trigger verification.
Answered in
Merkle Trees: How Git Detects Changes in MillisecondsGit hashes files into nested cryptographic trees to skip unchanged directories in one comparison, finding changes across millions of files faster than scanning.
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