fix(pgx): copyfrom imports (#1626)

Depending on the commands used in your `query.sql` the `copyfrom.go`
may end up with unused packge imports.

There is a patch for this problem that was merged in the #1386 PR.
However, it looks like some edge cases were left out of the fix.

This commit ensures that `buildImports` only has `copyfrom` queries
when called from `copyfromImports`.

internal/codegen/golang/imports.go

@@ -375,11 +375,14 @@ func (i *importer) queryImports(filename string) fileImports {
 }
 
 func (i *importer) copyfromImports() fileImports {
-	std, pkg := buildImports(i.Settings, i.Queries, func(name string) bool {
-		for _, q := range i.Queries {
-			if q.Cmd != metadata.CmdCopyFrom {
-				continue
-			}
+	copyFromQueries := make([]Query, 0, len(i.Queries))
+	for _, q := range i.Queries {
+		if q.Cmd == metadata.CmdCopyFrom {
+			copyFromQueries = append(copyFromQueries, q)
+		}
+	}
+	std, pkg := buildImports(i.Settings, copyFromQueries, func(name string) bool {
+		for _, q := range copyFromQueries {
 			if q.hasRetType() {
 				if strings.HasPrefix(q.Ret.Type(), name) {
 					return true

internal/endtoend/testdata/copyfrom_imports/postgresql/pgx/query.sql

@@ -6,3 +6,7 @@ INSERT INTO myschema.foo (a, b) VALUES ($1, $2);
 
 -- name: InsertSingleValue :exec
 INSERT INTO myschema.foo (a) VALUES ($1);
+
+-- name: DeleteValues :execresult
+DELETE
+FROM myschema.foo;