system: update doc commands and remove mutex

The mutex is not really doing anything, none of these methods make sense when called concurrently anyway. The copylocks analysis is still satisfied by the noCopy struct.

Signed-off-by: Ophestra <cat@gensokyo.uk>

system/op.go

@@ -1,164 +0,0 @@
-// Package system provides tools for safely interacting with the operating system.
-package system
-
-import (
-	"context"
-	"errors"
-	"log"
-	"strings"
-	"sync"
-)
-
-const (
-	// User type is reverted at final launcher exit.
-	User = EM << iota
-	// Process type is unconditionally reverted on exit.
-	Process
-
-	CM
-)
-
-// Criteria specifies types of Op to revert.
-type Criteria Enablement
-
-func (ec *Criteria) hasType(o Op) bool {
-	// nil criteria: revert everything except User
-	if ec == nil {
-		return o.Type() != User
-	}
-
-	return Enablement(*ec)&o.Type() != 0
-}
-
-// Op is a reversible system operation.
-type Op interface {
-	// Type returns Op's enablement type.
-	Type() Enablement
-
-	// apply the Op
-	apply(sys *I) error
-	// revert reverses the Op if criteria is met
-	revert(sys *I, ec *Criteria) error
-
-	Is(o Op) bool
-	Path() string
-	String() string
-}
-
-// TypeString returns the string representation of a type stored as an [Enablement].
-func TypeString(e Enablement) string {
-	switch e {
-	case User:
-		return "user"
-	case Process:
-		return "process"
-	default:
-		buf := new(strings.Builder)
-		buf.Grow(48)
-		if v := e &^ User &^ Process; v != 0 {
-			buf.WriteString(v.String())
-		}
-
-		for i := User; i < CM; i <<= 1 {
-			if e&i != 0 {
-				buf.WriteString(", " + TypeString(i))
-			}
-		}
-		return strings.TrimPrefix(buf.String(), ", ")
-	}
-}
-
-// New initialises sys with no-op verbose functions.
-func New(uid int) (sys *I) {
-	sys = new(I)
-	sys.uid = uid
-	return
-}
-
-// An I provides indirect bulk operating system interaction. I must not be copied.
-type I struct {
-	uid int
-	ops []Op
-	ctx context.Context
-
-	// whether sys has been reverted
-	state bool
-
-	lock sync.Mutex
-}
-
-func (sys *I) UID() int { return sys.uid }
-
-// Equal returns whether all [Op] instances held by v is identical to that of sys.
-func (sys *I) Equal(v *I) bool {
-	if v == nil || sys.uid != v.uid || len(sys.ops) != len(v.ops) {
-		return false
-	}
-
-	for i, o := range sys.ops {
-		if !o.Is(v.ops[i]) {
-			return false
-		}
-	}
-
-	return true
-}
-
-// Commit applies all [Op] held by [I] and reverts successful [Op] on first error encountered.
-// Commit must not be called more than once.
-func (sys *I) Commit(ctx context.Context) error {
-	sys.lock.Lock()
-	defer sys.lock.Unlock()
-
-	if sys.ctx != nil {
-		panic("sys instance committed twice")
-	}
-	sys.ctx = ctx
-
-	sp := New(sys.uid)
-	sp.ops = make([]Op, 0, len(sys.ops)) // prevent copies during commits
-	defer func() {
-		// sp is set to nil when all ops are applied
-		if sp != nil {
-			// rollback partial commit
-			msg.Verbosef("commit faulted after %d ops, rolling back partial commit", len(sp.ops))
-			if err := sp.Revert(nil); err != nil {
-				printJoinedError(log.Println, "cannot revert partial commit:", err)
-			}
-		}
-	}()
-
-	for _, o := range sys.ops {
-		if err := o.apply(sys); err != nil {
-			return err
-		} else {
-			// register partial commit
-			sp.ops = append(sp.ops, o)
-		}
-	}
-
-	// disarm partial commit rollback
-	sp = nil
-	return nil
-}
-
-// Revert reverts all [Op] meeting [Criteria] held by [I].
-func (sys *I) Revert(ec *Criteria) error {
-	sys.lock.Lock()
-	defer sys.lock.Unlock()
-
-	if sys.state {
-		panic("sys instance reverted twice")
-	}
-	sys.state = true
-
-	// collect errors
-	errs := make([]error, len(sys.ops))
-
-	for i := range sys.ops {
-		errs[i] = sys.ops[len(sys.ops)-i-1].revert(sys, ec)
-	}
-
-	// errors.Join filters nils
-	return errors.Join(errs...)
-}