[Go] use a Makefile to generate doc-go files (#479)

docs-go/Makefile

@@ -0,0 +1,10 @@
+WEAVE=$(HOME)/go/bin/weave 
+
+all: $(WEAVE) flows.md models.md
+
+$(WEAVE): ../go/internal/cmd/weave/*.go
+	go -C ../go install ./internal/cmd/weave
+
+%.md: %.src
+	$(WEAVE) $< > $@
+

go/internal/cmd/weave/weave.go

@@ -219,6 +219,7 @@ func cleanListing(text, indent string) string {
 	return strings.Join(lines, "\n")
 }
 
+// leadingTabs counts the number of tabs that start s.
 func leadingTabs(s string) int {
 	var i int
 	for i = 0; i < len(s); i++ {

go/internal/doc-snippets/doc.go

@@ -0,0 +1,19 @@
+// Copyright 2024 Google LLC
+//
+// 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.
+
+// Package snippets contains snippets that are incorporated into
+// documentation (see the docs-go directory under the repo root).
+package snippets
+
+//go:generate make -C ../../../docs-go