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
Docker does not respect the .dockerignore file when building from a tar.
Instead by default we'll make a local clone into a tmp directory and
build from there. Subsequent builds will reset the clone to match the
checkout.
Compared to building directly in the repo, we'll have reproducible
builds.
Compared to using a git archive:
1. .dockerignore is respected
2. We'll have faster builds - docker can be smarter about caching the
build context on subsequent builds from a directory
To build from the repo directly, set the build context to "." in the
config.
If there are uncommitted changes, we'll warn about them either being
included or ignored depending on whether we build from the clone.
Allow hosts to be tagged so we can have host specific env variables.
We might want host specific env variables for things like datacenter
specific tags or testing GC settings on a specific host.
Right now you either need to set up a separate role, or have the app
be host aware.
Now you can define tag env variables and assign those to hosts.
For example:
```
servers:
- 1.1.1.1
- 1.1.1.2: tag1
- 1.1.1.2: tag2
- 1.1.1.3: [ tag1, tag2 ]
env_tags:
tag1:
ENV1: value1
tag2:
ENV2: value2
```
The tag env supports the full env format, allowing you to set secret and
clear values.
When ssh options are set, they overwrite username and password passed as ssh builder uri. Passing part of uri for ssh-kit is fine, as it then properly extracts username and password and forwards it as host.ssh_options (in which case it's no longer empty)
Occasionally in CI things run slowly and it takes more that 1 second
for a cli test to run, so let's allow any value for the runtime in the
hook checks.
Extract Kamal::Commander::Specifics to deal with host and role setup and
ensure that primary hosts and roles always come first. This means that
in a rolling deploy we deploy to the primary ones first.
This will be important when we remove the healthcheck step as we want
to confirm the primary host can be deployed to before completing a
deployment for other roles.
By setting the hosts and roles all together in one place we can sort
the primary ones to the front without creating infinite loops.
