feat(tvix/store/protos): add Export r/6772

Export will traverse a given PathInfo structure, and write the contents
in NAR format to the passed Writer.
It uses directoryLookupFn and blobLookupFn to resolve references.

This is being moved over from nar-bridge. We need to keep the code there
around until we can bump go.mod to storev1 with this merged, but the
tests can already be moved entirely.

Change-Id: Ie0de3077b09344cafa00ff1e2ddb8b52e9e631bc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9602
Tested-by: BuildkiteCI
Reviewed-by: Brian McGee <brian@bmcgee.ie>
Autosubmit: flokli <flokli@flokli.de>

1 files changed, 0 insertions, 0 deletions

diff --git a/tvix/store/protos/testdata/symlink.nar b/tvix/store/protos/testdata/symlink.nar
new file mode 100644
index 0000000000..7990e4ad5b
--- /dev/null
+++ b/tvix/store/protos/testdata/symlink.nar
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