Add protobuf generated code for Go

.gitattributes

@@ -0,0 +1 @@
+*.pb.go linguist-generated

.github/workflows/generate.yml

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+#
+# Copyright 2022 The Sigstore Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Generate code
+
+permissions:
+  contents: read
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  generate_go:
+    name: Generate go code
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@93ea575cb5d8a053eaa0ac8fa3b40d7e05a33cc8 # v3
+
+    - name: Set up Go
+      uses: actions/setup-go@c4a742cab115ed795e34d4513e2cf7d472deb55f # v3.3.0
+
+    - name: Get dependencies
+      run: |
+        go generate -tags tools tools/tools.go
+
+    - name: Compile protobuf
+      run: |
+        make proto
+
+    - name: Ensure no files were modified as a result of the codegen
+      run: git update-index --refresh && git diff-index --quiet HEAD -- || git diff --exit-code

Makefile

@@ -0,0 +1,23 @@
+#
+# Copyright 2022 The Sigstore Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# bootstrap and install dev tools
+bootstrap:
+	go generate -tags tools tools/tools.go
+
+# generate Go protobuf code
+proto: 
+	@echo "Generating Protobuf files"
+	protoc -I=./protos --go_out=./protos --go_opt=paths=source_relative protos/*.proto

README.md

@@ -1 +1,15 @@
 # protobuf-specs
+
+This repository holds protobuf specifications for Sigstore messages.
+
+## Protobuf
+
+If you change protobuf definitions, you will need to regenerate the code by running the protocol buffer compiler on the changed `.proto` files.
+
+You will need [Go](https://www.golang.org/) installed on your machine. For local development, ensure that a [GOPATH](https://golang.org/doc/code.html#GOPATH) is set up. Then run, 
+
+```
+$ make proto
+```
+
+to generate the `*.pb.go` files under `protos/`.

go.mod

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+module github.com/sigstore/protobuf-specs
+
+go 1.18
+
+require google.golang.org/protobuf v1.28.1
+
+require github.com/google/trillian v1.5.0 // indirect

go.sum

@@ -0,0 +1,16 @@
+github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
+github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
+github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/trillian v1.5.0 h1:I5pIN18bKlXtlj1Tk919rQ3mWBU2BzNNR6JhLISGMB4=
+github.com/google/trillian v1.5.0/go.mod h1:2/gAIc+G1MUcErOPc+cSwHAQHZlGy+RYHjVGnhUQ3e8=
+golang.org/x/net v0.0.0-20220722155237-a158d28d115b h1:PxfKdU9lEEDYjdIzOtC4qFWgkU2rGHdKlKowJSMN9h0=
+golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f h1:v4INt8xihDGvnrfjMDVXGxw9wrfxYyCjk0KbXjhR55s=
+golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/genproto v0.0.0-20220706185917-7780775163c4 h1:7YDGQC/0sigNGzsEWyb9s72jTxlFdwVEYNJHbfQ+Dtg=
+google.golang.org/grpc v1.48.0 h1:rQOsyJ/8+ufEDJd/Gdsz7HG220Mh9HAhFHRGnIjda0w=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.28.1 h1:d0NfwRgPtno5B1Wa6L2DAG+KivqkdutMf1UhdNx175w=
+google.golang.org/protobuf v1.28.1/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=