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docs/src/dependency_updates.md

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+# Dependency updates
+
+Rust has the same problem as the node ecosystem, just a few magnitudes smaller:
+Dependency sprawl. GRM has a dozen direct dependencies, but over 150 transitive
+ones.
+
+To keep them up to date, there is a script:
+`depcheck/update-cargo-dependencies.py`. It updates direct dependencies to the
+latest stable version and updates transitive dependencies where possible. To run
+it, use `just update-dependencies`, which will create commits for each update.