internal/pkg: cure entry/exit notification

This enables cure status display without inspecting internal state.

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

internal/pkg/pkg.go

@@ -1826,6 +1826,10 @@ func (e *DependencyCureError) Error() string {
 
 // enterCure must be called before entering an [Artifact] implementation.
 func (c *Cache) enterCure(a Artifact, curesExempt bool) error {
+	if c.attr.Notify != nil {
+		c.attr.Notify <- true
+	}
+
 	if a.IsExclusive() {
 		c.exclMu.Lock()
 	}
@@ -1848,6 +1852,10 @@ func (c *Cache) enterCure(a Artifact, curesExempt bool) error {
 
 // exitCure must be called after exiting an [Artifact] implementation.
 func (c *Cache) exitCure(a Artifact, curesExempt bool) {
+	if c.attr.Notify != nil {
+		c.attr.Notify <- false
+	}
+
 	if a.IsExclusive() {
 		c.exclMu.Unlock()
 	}
@@ -2741,6 +2749,10 @@ func (c *Cache) Close() {
 	c.wg.Wait()
 	close(c.cures)
 	c.unlock()
+
+	if c.attr.Notify != nil {
+		close(c.attr.Notify)
+	}
 }
 
 // UnsupportedVariantError describes an on-disk cache with an extension variant
@@ -2768,6 +2780,8 @@ type CacheAttr struct {
 	Jobs int
 	// Preferred loadavg target, when applicable.
 	Load int
+	// Optional cure entry and exit notification.
+	Notify chan<- bool
 
 	// Omit the [lockedfile] lock.
 	skipLock bool