hooks: Add package support for extension stages

We aren't consuming this yet, but these pkg/hooks changes lay the
groundwork for future libpod changes to support post-exit hooks [1,2].

[1]: https://github.com/projectatomic/libpod/issues/730
[2]: https://github.com/opencontainers/runc/issues/1797

Signed-off-by: W. Trevor King <wking@tremily.us>

Closes: #758
Approved by: rhatdan

1 files changed, 5 insertions, 1 deletions

diff --git a/pkg/hooks/1.0.0/hook.go b/pkg/hooks/1.0.0/hook.go
index cf623ee42..77fbab5aa 100644
--- a/pkg/hooks/1.0.0/hook.go
+++ b/pkg/hooks/1.0.0/hook.go
@@ -31,7 +31,7 @@ func Read(content []byte) (hook *Hook, err error) {
 }
 
 // Validate performs load-time hook validation.
-func (hook *Hook) Validate() (err error) {
+func (hook *Hook) Validate(extensionStages []string) (err error) {
 	if hook == nil {
 		return errors.New("nil hook")
 	}
@@ -68,6 +68,10 @@ func (hook *Hook) Validate() (err error) {
 	}
 
 	validStages := map[string]bool{"prestart": true, "poststart": true, "poststop": true}
+	for _, stage := range extensionStages {
+		validStages[stage] = true
+	}
+
 	for _, stage := range hook.Stages {
 		if !validStages[stage] {
 			return fmt.Errorf("unknown stage %q", stage)