# `tools/ci/pkg/go`

This package parses diffs in `.bzl` files defining `go_repository` rules to determine what Go modules have changed for a build and ensure our code dependent on those modules is rebuilt.

## What determines a change

There must be a changed `sum` field, as indicated by a pair of lines starting with a corresponding `-` and `+`:

```
     go_repository(
         name = "com_github_pmezard_go_difflib",
@@ -1258,8 +1258,8 @@ def go():
         build_file_generation = "on",
         build_file_proto_mode = "disable_global",
         importpath = "gopkg.in/yaml.v3",
-        sum = "h1:B0J02caTR6tpSJozBJyiAzT6CtBzjclw4pgm9gg8Ys0=",
-        version = "v3.0.0-20190905181640-827449938966",
+        sum = "h1:XZx7nhd5GMaZpmDaEHFVafUZC7ya0fuo7cSJ3UCKYmM=",
+        version = "v3.0.0-20191120175047-4206685974f2",
     )
```

New `go_repository` rules will be excluded from this because they any new modules brought in via `go_repository` rules should also correspond to new `import` statements in Go code that would be picked up already.