Allow applications to be deployed without needing to set up a repository
in a remote Docker registry.
If the registry server starts with `localhost`, Kamal will start a local
docker registry on that port and push the app image to it.
Then when pulling the image onto the servers, we use net-ssh to forward
the that port from the app server to the deployment server.
This will allow the deployment server to pull the image from the
registry as if it were local, meaning we don't need to set up a cert.
Aliases are defined in the configuration file under the `aliases` key.
The configuration is a map of alias name to command. When we run the
command the we just do a literal replacement of the alias with the
string.
So if we have:
```yaml
aliases:
console: app exec -r console -i --reuse "rails console"
```
Then running `kamal console -r workers` will run the command
```sh
$ kamal app exec -r console -i --reuse "rails console" -r workers
```
Because of the order Thor parses the arguments, this allows us to
override the role from the alias command.
There might be cases where we need to munge the command a bit more but
that would involve getting into Thor command parsing internals,
which are complicated and possibly subject to change.
There's a chance that your aliases could conflict with future built-in
commands, but there's not likely to be many of those and if it happens
you'll get a validation error when you upgrade.
Thanks to @dhnaranjo for the idea!
Fixes:
```
ERROR (Net::SSH::Exception): Exception while executing on host example.com: could not settle on kex algorithm
Server kex preferences: curve25519-sha256@libssh.org,ext-info-s,kex-strict-s-v00@openssh.com
Client kex preferences: ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1```
add x25519 in Gemfile.lock
This includes a fix for a bug in the eviction thread that could cause
this error:
```
[ERROR (IOError): Exception while executing on host foo: closed stream]
```
See https://github.com/capistrano/sshkit/pull/534
