проектные команды и ссылки на источник

- заведён internal/source: уровни ссылаются друг на друга путём на диске
  или git-репозиторием, ревизия закрепляется хвостом #ref; клон делается
  заново и удаляется, кэша нет
- добавлены init, add, pull, list, check в проекте — манифест
  .conventions.toml, сборка копий по разу на компонент, маркер локальной
  части, READING.md рядом
- проверки формы развязаны с набором: принимают lang.Vocabulary, а язык
  копии узнаётся по строке о версии — манифеста рядом с ней нет

internal/suite/assemble.go

@@ -1,13 +1,22 @@
 package suite
 
-import "git.vakhrushev.me/av/convy/internal/doc"
+import (
+	"slices"
 
-// Component is what a copy is assembled for: one language, one stack, one kind
-// of application. Both axes may stay empty — a flat suite has no axes at all,
-// and a component of it selects the base layer and nothing else.
+	"git.vakhrushev.me/av/convy/internal/doc"
+)
+
+// Component is what a copy is assembled for: one language, one set of tools,
+// one kind of application. Both axes may stay empty — a flat suite has no axes
+// at all, and a component of it selects the base layer and nothing else.
+//
+// Each axis is a list because a component may take two stack layers at once:
+// sqlite and postgres in the schema topic hold together, being different tables
+// of one service. Two languages never hold together, and that the axis allows
+// the list anyway is a matter of one shape for both rather than a licence.
 type Component struct {
-	Lang  string
-	Stack string
+	Lang  []string
+	Stack []string
 }
 
 // Assemble picks the layers of a topic a component takes, in the order they go
@@ -34,10 +43,10 @@ func (s *Suite) Assemble(topic string, c Component) (taken, left []*doc.Document
 
 // fits reports whether a component takes a layer.
 func fits(d *doc.Document, c Component) bool {
-	if d.Front.Lang != "" && d.Front.Lang != c.Lang {
+	if d.Front.Lang != "" && !slices.Contains(c.Lang, d.Front.Lang) {
 		return false
 	}
-	if d.Front.Stack != "" && d.Front.Stack != c.Stack {
+	if d.Front.Stack != "" && !slices.Contains(c.Stack, d.Front.Stack) {
 		return false
 	}
 	return true