Implement Cobra CLI tooling, Viper config tooling (#336)

* start pulling out + replacing urfave and config

* replace many many instances of config

* move more stuff => viper

* properly remove urfave

* move some flags to root command

* add testrig commands to root

* alias config file keys

* start adding cli parsing tests

* reorder viper init

* remove config path alias

* fmt

* change config file keys to non-nested

* we're more or less in business now

* tidy up the common func

* go fmt

* get tests passing again

* add note about the cliparsing tests

* reorganize

* update docs with changes

* structure cmd dir better

* rename + move some files around

* fix dangling comma

vendor/github.com/spf13/afero/copyOnWriteFs.go

@@ -0,0 +1,326 @@
+package afero
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"syscall"
+	"time"
+)
+
+var _ Lstater = (*CopyOnWriteFs)(nil)
+
+// The CopyOnWriteFs is a union filesystem: a read only base file system with
+// a possibly writeable layer on top. Changes to the file system will only
+// be made in the overlay: Changing an existing file in the base layer which
+// is not present in the overlay will copy the file to the overlay ("changing"
+// includes also calls to e.g. Chtimes(), Chmod() and Chown()).
+//
+// Reading directories is currently only supported via Open(), not OpenFile().
+type CopyOnWriteFs struct {
+	base  Fs
+	layer Fs
+}
+
+func NewCopyOnWriteFs(base Fs, layer Fs) Fs {
+	return &CopyOnWriteFs{base: base, layer: layer}
+}
+
+// Returns true if the file is not in the overlay
+func (u *CopyOnWriteFs) isBaseFile(name string) (bool, error) {
+	if _, err := u.layer.Stat(name); err == nil {
+		return false, nil
+	}
+	_, err := u.base.Stat(name)
+	if err != nil {
+		if oerr, ok := err.(*os.PathError); ok {
+			if oerr.Err == os.ErrNotExist || oerr.Err == syscall.ENOENT || oerr.Err == syscall.ENOTDIR {
+				return false, nil
+			}
+		}
+		if err == syscall.ENOENT {
+			return false, nil
+		}
+	}
+	return true, err
+}
+
+func (u *CopyOnWriteFs) copyToLayer(name string) error {
+	return copyToLayer(u.base, u.layer, name)
+}
+
+func (u *CopyOnWriteFs) Chtimes(name string, atime, mtime time.Time) error {
+	b, err := u.isBaseFile(name)
+	if err != nil {
+		return err
+	}
+	if b {
+		if err := u.copyToLayer(name); err != nil {
+			return err
+		}
+	}
+	return u.layer.Chtimes(name, atime, mtime)
+}
+
+func (u *CopyOnWriteFs) Chmod(name string, mode os.FileMode) error {
+	b, err := u.isBaseFile(name)
+	if err != nil {
+		return err
+	}
+	if b {
+		if err := u.copyToLayer(name); err != nil {
+			return err
+		}
+	}
+	return u.layer.Chmod(name, mode)
+}
+
+func (u *CopyOnWriteFs) Chown(name string, uid, gid int) error {
+	b, err := u.isBaseFile(name)
+	if err != nil {
+		return err
+	}
+	if b {
+		if err := u.copyToLayer(name); err != nil {
+			return err
+		}
+	}
+	return u.layer.Chown(name, uid, gid)
+}
+
+func (u *CopyOnWriteFs) Stat(name string) (os.FileInfo, error) {
+	fi, err := u.layer.Stat(name)
+	if err != nil {
+		isNotExist := u.isNotExist(err)
+		if isNotExist {
+			return u.base.Stat(name)
+		}
+		return nil, err
+	}
+	return fi, nil
+}
+
+func (u *CopyOnWriteFs) LstatIfPossible(name string) (os.FileInfo, bool, error) {
+	llayer, ok1 := u.layer.(Lstater)
+	lbase, ok2 := u.base.(Lstater)
+
+	if ok1 {
+		fi, b, err := llayer.LstatIfPossible(name)
+		if err == nil {
+			return fi, b, nil
+		}
+
+		if !u.isNotExist(err) {
+			return nil, b, err
+		}
+	}
+
+	if ok2 {
+		fi, b, err := lbase.LstatIfPossible(name)
+		if err == nil {
+			return fi, b, nil
+		}
+		if !u.isNotExist(err) {
+			return nil, b, err
+		}
+	}
+
+	fi, err := u.Stat(name)
+
+	return fi, false, err
+}
+
+func (u *CopyOnWriteFs) SymlinkIfPossible(oldname, newname string) error {
+	if slayer, ok := u.layer.(Linker); ok {
+		return slayer.SymlinkIfPossible(oldname, newname)
+	}
+
+	return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: ErrNoSymlink}
+}
+
+func (u *CopyOnWriteFs) ReadlinkIfPossible(name string) (string, error) {
+	if rlayer, ok := u.layer.(LinkReader); ok {
+		return rlayer.ReadlinkIfPossible(name)
+	}
+
+	if rbase, ok := u.base.(LinkReader); ok {
+		return rbase.ReadlinkIfPossible(name)
+	}
+
+	return "", &os.PathError{Op: "readlink", Path: name, Err: ErrNoReadlink}
+}
+
+func (u *CopyOnWriteFs) isNotExist(err error) bool {
+	if e, ok := err.(*os.PathError); ok {
+		err = e.Err
+	}
+	if err == os.ErrNotExist || err == syscall.ENOENT || err == syscall.ENOTDIR {
+		return true
+	}
+	return false
+}
+
+// Renaming files present only in the base layer is not permitted
+func (u *CopyOnWriteFs) Rename(oldname, newname string) error {
+	b, err := u.isBaseFile(oldname)
+	if err != nil {
+		return err
+	}
+	if b {
+		return syscall.EPERM
+	}
+	return u.layer.Rename(oldname, newname)
+}
+
+// Removing files present only in the base layer is not permitted. If
+// a file is present in the base layer and the overlay, only the overlay
+// will be removed.
+func (u *CopyOnWriteFs) Remove(name string) error {
+	err := u.layer.Remove(name)
+	switch err {
+	case syscall.ENOENT:
+		_, err = u.base.Stat(name)
+		if err == nil {
+			return syscall.EPERM
+		}
+		return syscall.ENOENT
+	default:
+		return err
+	}
+}
+
+func (u *CopyOnWriteFs) RemoveAll(name string) error {
+	err := u.layer.RemoveAll(name)
+	switch err {
+	case syscall.ENOENT:
+		_, err = u.base.Stat(name)
+		if err == nil {
+			return syscall.EPERM
+		}
+		return syscall.ENOENT
+	default:
+		return err
+	}
+}
+
+func (u *CopyOnWriteFs) OpenFile(name string, flag int, perm os.FileMode) (File, error) {
+	b, err := u.isBaseFile(name)
+	if err != nil {
+		return nil, err
+	}
+
+	if flag&(os.O_WRONLY|os.O_RDWR|os.O_APPEND|os.O_CREATE|os.O_TRUNC) != 0 {
+		if b {
+			if err = u.copyToLayer(name); err != nil {
+				return nil, err
+			}
+			return u.layer.OpenFile(name, flag, perm)
+		}
+
+		dir := filepath.Dir(name)
+		isaDir, err := IsDir(u.base, dir)
+		if err != nil && !os.IsNotExist(err) {
+			return nil, err
+		}
+		if isaDir {
+			if err = u.layer.MkdirAll(dir, 0777); err != nil {
+				return nil, err
+			}
+			return u.layer.OpenFile(name, flag, perm)
+		}
+
+		isaDir, err = IsDir(u.layer, dir)
+		if err != nil {
+			return nil, err
+		}
+		if isaDir {
+			return u.layer.OpenFile(name, flag, perm)
+		}
+
+		return nil, &os.PathError{Op: "open", Path: name, Err: syscall.ENOTDIR} // ...or os.ErrNotExist?
+	}
+	if b {
+		return u.base.OpenFile(name, flag, perm)
+	}
+	return u.layer.OpenFile(name, flag, perm)
+}
+
+// This function handles the 9 different possibilities caused
+// by the union which are the intersection of the following...
+//  layer: doesn't exist, exists as a file, and exists as a directory
+//  base:  doesn't exist, exists as a file, and exists as a directory
+func (u *CopyOnWriteFs) Open(name string) (File, error) {
+	// Since the overlay overrides the base we check that first
+	b, err := u.isBaseFile(name)
+	if err != nil {
+		return nil, err
+	}
+
+	// If overlay doesn't exist, return the base (base state irrelevant)
+	if b {
+		return u.base.Open(name)
+	}
+
+	// If overlay is a file, return it (base state irrelevant)
+	dir, err := IsDir(u.layer, name)
+	if err != nil {
+		return nil, err
+	}
+	if !dir {
+		return u.layer.Open(name)
+	}
+
+	// Overlay is a directory, base state now matters.
+	// Base state has 3 states to check but 2 outcomes:
+	// A. It's a file or non-readable in the base (return just the overlay)
+	// B. It's an accessible directory in the base (return a UnionFile)
+
+	// If base is file or nonreadable, return overlay
+	dir, err = IsDir(u.base, name)
+	if !dir || err != nil {
+		return u.layer.Open(name)
+	}
+
+	// Both base & layer are directories
+	// Return union file (if opens are without error)
+	bfile, bErr := u.base.Open(name)
+	lfile, lErr := u.layer.Open(name)
+
+	// If either have errors at this point something is very wrong. Return nil and the errors
+	if bErr != nil || lErr != nil {
+		return nil, fmt.Errorf("BaseErr: %v\nOverlayErr: %v", bErr, lErr)
+	}
+
+	return &UnionFile{Base: bfile, Layer: lfile}, nil
+}
+
+func (u *CopyOnWriteFs) Mkdir(name string, perm os.FileMode) error {
+	dir, err := IsDir(u.base, name)
+	if err != nil {
+		return u.layer.MkdirAll(name, perm)
+	}
+	if dir {
+		return ErrFileExists
+	}
+	return u.layer.MkdirAll(name, perm)
+}
+
+func (u *CopyOnWriteFs) Name() string {
+	return "CopyOnWriteFs"
+}
+
+func (u *CopyOnWriteFs) MkdirAll(name string, perm os.FileMode) error {
+	dir, err := IsDir(u.base, name)
+	if err != nil {
+		return u.layer.MkdirAll(name, perm)
+	}
+	if dir {
+		// This is in line with how os.MkdirAll behaves.
+		return nil
+	}
+	return u.layer.MkdirAll(name, perm)
+}
+
+func (u *CopyOnWriteFs) Create(name string) (File, error) {
+	return u.OpenFile(name, os.O_CREATE|os.O_TRUNC|os.O_RDWR, 0666)
+}