build

diff: do not add excessive number of context lines to last unified-di… #12306

Job	Run time
Build jj-lib without Git support	43s
build (ubuntu-latest)	4m 8s
Check protos	26s
build (macos-14)	3m 48s
Check formatting	15s
build (windows-latest)	8m 31s
build (ubuntu-latest, --all-features)	4m 58s
cargo-deny (advisories)	22s
cargo-deny (bans licenses sources)	29s
Clippy check	2m 31s
Check that MkDocs can build the docs	23s
Check that MkDocs can build the docs with Poetry 1.8	24s
	26m 58s

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