V2 API Version Support

* Update blang/semver to allow ParseTolerant() support
* Provide helper functions for API handlers to obtain client's 'version'
  path variable focused on API endpoint tree: libpod vs. compat
* Introduce new errors:
  * version not given in path, endpoints may determine if this is a hard
    error (ErrVersionNotGiven)
  * given version not supported (ErrVersionNotSupported), only a soft
    error if the handler is going to hijack the connection
* Added unit tests for version parsing
* bindings check version on connect:
  * client <= Server API version connection is continued
  * client >= Server API version connection fails

Signed-off-by: Jhon Honce <jhonce@redhat.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/pkg/api/handlers/compat/ping.go b/pkg/api/handlers/compat/ping.go
index 6e77e270f..abee3d8e8 100644
--- a/pkg/api/handlers/compat/ping.go
+++ b/pkg/api/handlers/compat/ping.go
@@ -5,22 +5,22 @@ import (
 	"net/http"
 
 	"github.com/containers/buildah"
-	"github.com/containers/libpod/pkg/api/handlers"
+	"github.com/containers/libpod/pkg/api/handlers/utils"
 )
 
 // Ping returns headers to client about the service
 //
 // This handler must always be the same for the compatibility and libpod URL trees!
 // Clients will use the Header availability to test which backend engine is in use.
+// Note: Additionally handler supports GET and HEAD methods
 func Ping(w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("API-Version", handlers.DefaultApiVersion)
+	w.Header().Set("API-Version", utils.ApiVersion[utils.CompatTree][utils.CurrentApiVersion].String())
 	w.Header().Set("BuildKit-Version", "")
 	w.Header().Set("Docker-Experimental", "true")
 	w.Header().Set("Cache-Control", "no-cache")
 	w.Header().Set("Pragma", "no-cache")
 
-	// API-Version and Libpod-API-Version may not always be equal
-	w.Header().Set("Libpod-API-Version", handlers.DefaultApiVersion)
+	w.Header().Set("Libpod-API-Version", utils.ApiVersion[utils.LibpodTree][utils.CurrentApiVersion].String())
 	w.Header().Set("Libpod-Buildha-Version", buildah.Version)
 	w.WriteHeader(http.StatusOK)