Improve blame timestamp handling #2220

Job	Run time
Rustfmt	11s
Unit tests (macos-latest, aarch64-apple-darwin, false)	2m 15s
Code coverage	3m 9s
Unit tests (macos-12, x86_64-apple-darwin, false)	3m 33s
Clippy	44s
Integration tests (macos-latest)	1m 58s
Unit tests (windows-latest, x86_64-pc-windows-msvc, false)	5m 27s
Integration tests (ubuntu-latest)	2m 15s
Unit tests (ubuntu-latest, x86_64-unknown-linux-gnu, false)	2m 41s
Unit tests (ubuntu-latest, x86_64-unknown-linux-musl, true)	3m 15s
Unit tests (ubuntu-latest, i686-unknown-linux-gnu, true)	3m 1s
Unit tests (ubuntu-latest, arm-unknown-linux-gnueabihf, true)	3m 17s
Unit tests (ubuntu-latest, aarch64-unknown-linux-gnu, true)	3m 16s
	35m 2s

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