Add option to ignore nested git repositories #2603

Job	Run time
test (pinned, ubuntu-latest, 1.74.0)	1m 5s
rustfmt	12s
docs	10s
test (stable, ubuntu-latest, stable)	52s
test (beta, ubuntu-latest, beta)	1m 15s
test (nightly, ubuntu-latest, nightly)	1m 3s
test (stable-musl, ubuntu-latest, stable, x86_64-unknown-linux-musl)	3m 47s
test (stable-x86, ubuntu-latest, stable, i686-unknown-linux-gnu)	1m 28s
test (stable-aarch64, ubuntu-latest, stable, aarch64-unknown-linux-gnu)	3m 21s
test (stable-arm-gnueabihf, ubuntu-latest, stable, armv7-unknown-linux-gnueabihf)	3m 13s
test (stable-arm-musleabihf, ubuntu-latest, stable, armv7-unknown-linux-musleabihf)	3m 39s
test (stable-arm-musleabi, ubuntu-latest, stable, armv7-unknown-linux-musleabi)	4m 4s
test (stable-powerpc64, ubuntu-latest, stable, powerpc64-unknown-linux-gnu)	3m 7s
test (stable-s390x, ubuntu-latest, stable, s390x-unknown-linux-gnu)	3m 5s
test (macos, macos-latest, nightly)	1m 5s
test (win-msvc, windows-2022, nightly)	1m 56s
test (win-gnu, windows-2022, nightly-x86_64-gnu)	2m 30s
	35m 52s

Provide feedback