fix 0.8 to 1.0 conversion when legacy merge keys

go.sum

@@ -53,6 +53,7 @@ github.com/sergi/go-diff v1.0.0/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAm
 github.com/spf13/pflag v1.0.3/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/vinzenz/yaml v0.0.0-20170920082545-91409cdd725d h1:3wDi6J5APMqaHBVPuVd7RmHD2gRTfqbdcVSpCNoUWtk=
 github.com/vinzenz/yaml v0.0.0-20170920082545-91409cdd725d/go.mod h1:mb5taDqMnJiZNRQ3+02W2IFG+oEz1+dTuCXkp4jpkfo=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=

yaml/converter/legacy/internal/config.go

@@ -39,6 +39,13 @@ type Config struct {
 // Convert converts the yaml configuration file from
 // the legacy format to the 1.0+ format.
 func Convert(d []byte) ([]byte, error) {
+	// hack: this is a hack to support teams migrating
+	// from 0.8 to 1.0 that are using yaml merge keys.
+	// it can be removed in a future version.
+	if hasMergeKeys(d) {
+		d, _ = expandMergeKeys(d)
+	}
+
 	from := new(Config)
 	err := yaml.Unmarshal(d, from)
 

yaml/converter/legacy/internal/yaml.go

@@ -0,0 +1,28 @@
+// Copyright 2019 Drone.IO Inc. All rights reserved.
+// Use of this source code is governed by the Drone Non-Commercial License
+// that can be found in the LICENSE file.
+
+package yaml
+
+import (
+	"bytes"
+
+	"github.com/vinzenz/yaml"
+)
+
+// this is a helper function that expands merge keys
+func expandMergeKeys(b []byte) ([]byte, error) {
+	v := map[interface{}]interface{}{}
+	if err := yaml.Unmarshal(b, v); err != nil {
+		return b, err
+	}
+	o, err := yaml.Marshal(v)
+	if err != nil {
+		return b, err
+	}
+	return o, nil
+}
+
+func hasMergeKeys(b []byte) bool {
+	return bytes.Contains(b, []byte("<<:"))
+}