feat: absolute imports (#63)

* feat: go-like import style

jb now creates a directory structure inside of vendor/ that is similar to how go
does (github.com/grafana/jsonnet-libs). This is reflected in the final import
paths, which means they will be go-like

* refactor(spec/deps): named regexs

* feat: make goImportStyle configurable

Defaults to off, can be enabled in `jsonnetfile.json`

* fix: integration test

* doc: license headers

* fix(deps): remove GO_IMPORT_STYLE

not an option anymore, will always do so and symlink

* feat: symlink to legacy location

* feat: allow to disable legacy links

* fix(test): legacyImports in integration tests

* fix(spec): test

* fix: respect legacyName aliases

It was possible to alias packages by changing `name` previously.

While names are now absolute (and computed), legacy links should still respect
old aliases to avoid breaking code.

* fix(test): integration

* fix(init): keep legacyImports enabled for now

* feat: rewrite imports

adds a command to automatically rewrite imports from legacy to absolute style

* fix(tool): rewrite confused by prefixing packages

When a package was a prefix of another one, it broke.
Fixed that by using a proper regular expression. Added a test to make sure it
works as expected

* Update cmd/jb/init.go

* fix: exclude local packages from legacy linking

They actually still use the old style, which is fine. LegacyLinking
messed them up, but from now on it just ignores symlinks that match a localPackage.

spec/deps/dependencies_test.go

@@ -0,0 +1,70 @@
+// Copyright 2018 jsonnet-bundler 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.
+package deps
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseDependency(t *testing.T) {
+	const testFolder = "test/jsonnet/foobar"
+	err := os.MkdirAll(testFolder, os.ModePerm)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll("test")
+
+	tests := []struct {
+		name string
+		path string
+		want *Dependency
+	}{
+		{
+			name: "Empty",
+			path: "",
+			want: nil,
+		},
+		{
+			name: "Invalid",
+			path: "github.com/foo",
+			want: nil,
+		},
+		{
+			name: "local",
+			path: testFolder,
+			want: &Dependency{
+				Source: Source{
+					LocalSource: &Local{
+						Directory: "test/jsonnet/foobar",
+					},
+				},
+				Version: "",
+			},
+		},
+	}
+	for _, tt := range tests {
+		_ = t.Run(tt.name, func(t *testing.T) {
+			dependency := Parse("", tt.path)
+
+			if tt.path == "" {
+				assert.Nil(t, dependency)
+			} else {
+				assert.Equal(t, tt.want, dependency)
+			}
+		})
+	}
+}