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.

cmd/jb/rewrite.go

@@ -0,0 +1,36 @@
+// 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 main
+
+import (
+	"path/filepath"
+
+	kingpin "gopkg.in/alecthomas/kingpin.v2"
+
+	"github.com/jsonnet-bundler/jsonnet-bundler/pkg/jsonnetfile"
+	"github.com/jsonnet-bundler/jsonnet-bundler/tool/rewrite"
+)
+
+func rewriteCommand(dir, vendorDir string) int {
+	locks, err := jsonnetfile.Load(filepath.Join(dir, jsonnetfile.LockFile))
+	if err != nil {
+		kingpin.Fatalf("Failed to load lockFile: %s.\nThe locks are required to compute the new import names. Make sure to run `jb install` first.", err)
+	}
+
+	if err := rewrite.Rewrite(dir, vendorDir, locks.Dependencies); err != nil {
+		kingpin.FatalIfError(err, "")
+	}
+
+	return 0
+}