Update bazel cpp_jsonnet reference from update_cpp_jsonnet.sh

Teach `update_cpp_jsonnet.sh` to update the cpp_jsonnet reference in
`bazel/repositories.bzl` too.

bazel/repositories.bzl

@@ -3,6 +3,10 @@ load(
     "http_archive",
 )
 
+# NB: update_cpp_jsonnet.sh looks for these.
+CPP_JSONNET_SHA256 = "82d3cd35de8ef230d094b60a30e7659f415c350b0aa2bd62162cf2afdf163959"
+CPP_JSONNET_GITHASH = "90cad75dcc2eafdcf059c901169d36539dc8a699"
+
 def jsonnet_go_repositories():
     http_archive(
         name = "io_bazel_rules_go",
@@ -23,7 +27,7 @@ def jsonnet_go_repositories():
     )
     http_archive(
         name = "cpp_jsonnet",
-        sha256 = "82d3cd35de8ef230d094b60a30e7659f415c350b0aa2bd62162cf2afdf163959",
-        strip_prefix = "jsonnet-90cad75dcc2eafdcf059c901169d36539dc8a699",
-        urls = ["https://github.com/google/jsonnet/archive/90cad75dcc2eafdcf059c901169d36539dc8a699.tar.gz"],
+        sha256 = CPP_JSONNET_SHA256,
+        strip_prefix = "jsonnet-%s" % CPP_JSONNET_GITHASH,
+        urls = ["https://github.com/google/jsonnet/archive/%s.tar.gz" % CPP_JSONNET_GITHASH],
     )

update_cpp_jsonnet.sh

@@ -8,9 +8,20 @@ set -x
 cd cpp-jsonnet
 git checkout master
 git pull
+hash=$(git rev-parse HEAD)
 cd ..
 go run cmd/dumpstdlibast/dumpstdlibast.go cpp-jsonnet/stdlib/std.jsonnet > astgen/stdast.go
 
+sha256=$(curl -fL https://github.com/google/jsonnet/archive/$hash.tar.gz | shasum -a 256 | awk '{print $1}')
+
+sed -i.bak \
+    -e "s/CPP_JSONNET_SHA256 = .*/CPP_JSONNET_SHA256 = \"$sha256\"/;" \
+    -e "s/CPP_JSONNET_GITHASH = .*/CPP_JSONNET_GITHASH = \"$hash\"/;" \
+    bazel/repositories.bzl
+
+# NB: macOS sed doesn't support -i without arg. This is the easy workaround.
+rm bazel/repositories.bzl.bak
+
 set +x
 echo
 echo -e "\033[1mUpdate completed. Please check if any tests are broken and fix any encountered issues.\033[0m"