Release file: support Version field

https://wiki.debian.org/DebianRepository/Format#Version

The Version field, if specified, shall be the version of the release.
On the other hand, if not set or set to an empty value, the Version
field will not be included in the Release file.

Signed-off-by: Zhang Xiao <xiao.zhang@windriver.com>

cmd/publish_snapshot.go

@@ -158,6 +158,10 @@ func aptlyPublishSnapshotOrRepo(cmd *commander.Command, args []string) error {
 		published.MultiDist = context.Flags().Lookup("multi-dist").Value.Get().(bool)
 	}
 
+	if context.Flags().IsSet("version") {
+		published.Version = context.Flags().Lookup("version").Value.String()
+	}
+
 	duplicate := collectionFactory.PublishedRepoCollection().CheckDuplicate(published)
 	if duplicate != nil {
 		_ = collectionFactory.PublishedRepoCollection().LoadComplete(duplicate, collectionFactory)
@@ -252,6 +256,7 @@ Example:
 	cmd.Flag.Bool("force-overwrite", false, "overwrite files in package pool in case of mismatch")
 	cmd.Flag.Bool("acquire-by-hash", false, "provide index files by hash")
 	cmd.Flag.String("signed-by", "", "an optional field containing a comma separated list of OpenPGP key fingerprints to be used for validating the next Release file")
+	cmd.Flag.String("version", "", "version of the release")
 	cmd.Flag.Bool("multi-dist", false, "enable multiple packages with the same filename in different distributions")
 
 	return cmd