feat(tools/tvlc): pass list of derivations to depot-scanner

You can now provide a list of Nix derivations to tvlc to get a git worktree + sparse-checkout containing only the paths needed to build the specified derivations.

Known bugs: even though //third_party is only passed to readdir(), git doesn't know this and includes all of //third_party/*.

Change-Id: I9dccebd3fbff4bb04ebd568175cf0a7e37d71ab3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1826
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

tools/tvlc/common.sh

@@ -3,9 +3,12 @@
 set -eu
 set -o pipefail
 
+source path-scripts
+
 XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"
 tvlc_root="$XDG_DATA_HOME/tvlc"
 
+nice_checkout_root=
 if [ -f "$tvlc_root"/nice_checkout_root ]; then
   nice_checkout_root="$(cat "$tvlc_root"/nice_checkout_root)"
 fi