Refactor repository layout and convert build system to Mage.

This commit implements a massive refactor of the repository, and
moves the build system over to use Mage (magefile.org) which should
allow seamless building across multiple platforms.

vendor/github.com/magefile/mage/mg/deps.go

@@ -0,0 +1,166 @@
+package mg
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+
+	"github.com/magefile/mage/types"
+)
+
+type onceMap struct {
+	mu *sync.Mutex
+	m  map[string]*onceFun
+}
+
+func (o *onceMap) LoadOrStore(s string, one *onceFun) *onceFun {
+	defer o.mu.Unlock()
+	o.mu.Lock()
+
+	existing, ok := o.m[s]
+	if ok {
+		return existing
+	}
+	o.m[s] = one
+	return one
+}
+
+var onces = &onceMap{
+	mu: &sync.Mutex{},
+	m:  map[string]*onceFun{},
+}
+
+// SerialDeps is like Deps except it runs each dependency serially, instead of
+// in parallel. This can be useful for resource intensive dependencies that
+// shouldn't be run at the same time.
+func SerialDeps(fns ...interface{}) {
+	checkFns(fns)
+	ctx := context.Background()
+	for _, f := range fns {
+		runDeps(ctx, f)
+	}
+}
+
+// SerialCtxDeps is like CtxDeps except it runs each dependency serially,
+// instead of in parallel. This can be useful for resource intensive
+// dependencies that shouldn't be run at the same time.
+func SerialCtxDeps(ctx context.Context, fns ...interface{}) {
+	checkFns(fns)
+	for _, f := range fns {
+		runDeps(ctx, f)
+	}
+}
+
+// CtxDeps runs the given functions as dependencies of the calling function.
+// Dependencies must only be of type: github.com/magefile/mage/types.FuncType.
+// The function calling Deps is guaranteed that all dependent functions will be
+// run exactly once when Deps returns.  Dependent functions may in turn declare
+// their own dependencies using Deps. Each dependency is run in their own
+// goroutines. Each function is given the context provided if the function
+// prototype allows for it.
+func CtxDeps(ctx context.Context, fns ...interface{}) {
+	checkFns(fns)
+	runDeps(ctx, fns...)
+}
+
+// runDeps assumes you've already called checkFns.
+func runDeps(ctx context.Context, fns ...interface{}) {
+	mu := &sync.Mutex{}
+	var errs []string
+	var exit int
+	wg := &sync.WaitGroup{}
+	for _, f := range fns {
+		fn := addDep(ctx, f)
+		wg.Add(1)
+		go func() {
+			defer func() {
+				if v := recover(); v != nil {
+					mu.Lock()
+					if err, ok := v.(error); ok {
+						exit = changeExit(exit, ExitStatus(err))
+					} else {
+						exit = changeExit(exit, 1)
+					}
+					errs = append(errs, fmt.Sprint(v))
+					mu.Unlock()
+				}
+				wg.Done()
+			}()
+			if err := fn.run(); err != nil {
+				mu.Lock()
+				errs = append(errs, fmt.Sprint(err))
+				exit = changeExit(exit, ExitStatus(err))
+				mu.Unlock()
+			}
+		}()
+	}
+
+	wg.Wait()
+	if len(errs) > 0 {
+		panic(Fatal(exit, strings.Join(errs, "\n")))
+	}
+}
+
+func checkFns(fns []interface{}) {
+	for _, f := range fns {
+		if err := types.FuncCheck(f); err != nil {
+			panic(err)
+		}
+	}
+}
+
+// Deps runs the given functions with the default runtime context
+func Deps(fns ...interface{}) {
+	CtxDeps(context.Background(), fns...)
+}
+
+func changeExit(old, new int) int {
+	if new == 0 {
+		return old
+	}
+	if old == 0 {
+		return new
+	}
+	if old == new {
+		return old
+	}
+	// both different and both non-zero, just set
+	// exit to 1. Nothing more we can do.
+	return 1
+}
+
+func addDep(ctx context.Context, f interface{}) *onceFun {
+	var fn func(context.Context) error
+	if fn = types.FuncTypeWrap(f); fn == nil {
+		// should be impossible, since we already checked this
+		panic("attempted to add a dep that did not match required type")
+	}
+
+	n := name(f)
+	of := onces.LoadOrStore(n, &onceFun{
+		fn:  fn,
+		ctx: ctx,
+	})
+	return of
+}
+
+func name(i interface{}) string {
+	return runtime.FuncForPC(reflect.ValueOf(i).Pointer()).Name()
+}
+
+type onceFun struct {
+	once sync.Once
+	fn   func(context.Context) error
+	ctx  context.Context
+}
+
+func (o *onceFun) run() error {
+	var err error
+	o.once.Do(func() {
+		err = o.fn(o.ctx)
+	})
+	return err
+}

vendor/github.com/magefile/mage/mg/errors.go

@@ -0,0 +1,51 @@
+package mg
+
+import (
+	"errors"
+	"fmt"
+)
+
+type fatalErr struct {
+	code int
+	error
+}
+
+func (f fatalErr) ExitStatus() int {
+	return f.code
+}
+
+type exitStatus interface {
+	ExitStatus() int
+}
+
+// Fatal returns an error that will cause mage to print out the
+// given args and exit with the given exit code.
+func Fatal(code int, args ...interface{}) error {
+	return fatalErr{
+		code:  code,
+		error: errors.New(fmt.Sprint(args...)),
+	}
+}
+
+// Fatalf returns an error that will cause mage to print out the
+// given message and exit with an exit code of 1.
+func Fatalf(code int, format string, args ...interface{}) error {
+	return fatalErr{
+		code:  code,
+		error: fmt.Errorf(format, args...),
+	}
+}
+
+// ExitStatus queries the error for an exit status.  If the error is nil, it
+// returns 0.  If the error does not implement ExitStatus() int, it returns 1.
+// Otherwise it retiurns the value from ExitStatus().
+func ExitStatus(err error) int {
+	if err == nil {
+		return 0
+	}
+	exit, ok := err.(exitStatus)
+	if !ok {
+		return 1
+	}
+	return exit.ExitStatus()
+}

vendor/github.com/magefile/mage/mg/runtime.go

@@ -0,0 +1,36 @@
+package mg
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+// CacheEnv is the environment variable that users may set to change the
+// location where mage stores its compiled binaries.
+const CacheEnv = "MAGEFILE_CACHE"
+
+// verboseEnv is the environment variable that indicates the user requested
+// verbose mode when running a magefile.
+const verboseEnv = "MAGEFILE_VERBOSE"
+
+// Verbose reports whether a magefile was run with the verbose flag.
+func Verbose() bool {
+	return os.Getenv(verboseEnv) != ""
+}
+
+// CacheDir returns the directory where mage caches compiled binaries.  It
+// defaults to $HOME/.magefile, but may be overridden by the MAGEFILE_CACHE
+// environment variable.
+func CacheDir() string {
+	d := os.Getenv(CacheEnv)
+	if d != "" {
+		return d
+	}
+	switch runtime.GOOS {
+	case "windows":
+		return filepath.Join(os.Getenv("HOMEDRIVE"), os.Getenv("HOMEPATH"), "magefile")
+	default:
+		return filepath.Join(os.Getenv("HOME"), ".magefile")
+	}
+}