In my very large Rust-based project of about 100k lines of code, 100 direct dependencies, and 800 total dependencies, I always require version="*" for each dependency, except for specific ones that either I cannot or don't want to upgrade.

Crucially, I also commit my Cargo.lock, as the Cargo manual recommends.

I normally build with cargo --locked. Periodically, I will do a cargo update and run cargo outdated so that I'm able to see if there are specific packages keeping me at older versions.

To upgrade a specific package, I can just remove it's record directly from Cargo.lock and then do a regular cargo build.

This works very well!

Advantages

• I minimize my number of dependencies, and therefor build times
• I keep my personal ecosystem from falling too far behind that of crates.io
• I rarely wind up with a situation where I have two dependencies that depend on a different symbol version
• I don't have to change a version in all of my many Cargo.tomls

Disadvantages

• I cannot publish my large repository to a wider audience (but that will never happen for this repository)
• People who see my code start feeling ill and start shifting their eyes nervously.