Parameters are the customizable fields defining ksonnet components. For
example, replica count, component name, or deployment image.

Parameters are also able to be defined separately across environments.
Meaning, this supports features to allow a "development" environment to
only run a single replication instance for it's components, whereas
allowing a "production" environment to run more replication instances to
meet heavier production load demands.

'ks param set' is defined as follows:
  'ks param set <component-name> <param-key> <param-value>'

Examples:

Updates the replica count of the 'guestbook' component to 4.
  'ks param set guestbook replicas 4'

Updates the replica count of the 'guestbook' component to 2 for the
environment 'dev'
  'ks param set guestbook replicas 2 --env=dev'

The goal of this commit is to add an interface to `metadata.Manager`
that allows retrieving of all environment params:
`getEnvironmentParams(envName)`.

This is done by:

1. Adding functionality to the snippet parser to get all environment
params out of the snippet read from
`environments/<env>/params.libsonnet`

2. Adding functionality to the snippet parser to get all component
params out of the snippet read from `components/params.libsonnet`

3. Having the `metadata.Manager` implementation handle the 'joining' of
params from 1) and 2), and returning that result.

This commit will add an interface `SetEnvironmentParams` to
metadata.Manager that allows setting of env params.

Also implements the logic for parsing the jsonnet snippet to
append / modify params in simple env param schemas. It will:

1. Update the params if the component exists in the jsonnet
snippet.
2. Add the component if it does not exist.

This commit will add an interface `GetComponentParams` to
metadata.Manager that returns a map of parameters for the passed in
component.

Also implements the logic for parsing the jsonnet snippet to retrieve
the parameters.

This functionality will later support new commands to list parameters.

This commit will:

1. Add an interface `SetComponentParams` to metadata.Manager that takes
a list of parameters and sets those fields for the given component.

2. Add the jsonnet snippet manipulation logic that does the
'setting'. Parameters are set by:

a. Keeping track of the parameters that are to be modified / added --
this defaults to the parameters provided to us.
b. Discovering the current parameters in the existing snippet.
c. Adding any parameters from (b) that is not in (a).
d. Swapping out the old parameters with (c) in the snippet based on
the location text span, and returning the new snippet.

This commit will append both mandatory and optional  prototype
parameters to the component params.libsonnet file on `ks gen foo ...`.

Default values will be used for optional params where the user does not
specify flags to `ks gen foo ...`.

Because we are trying to append to jsonnet, we will have to traverse the
AST to first identify the location of where to insert the new component
params. New components will be inserted at the bottom of the components
object, with the params ordered alphabetically.

We are currently parsing system prototypes using the default TextMate
snippet which does not take into account the translation of params of
format `import 'param://foo`. The jsonnet snippet parser does take this
into account.

Rewrite system prototype params from `${foo}` format to `import
'param://foo'` so that they can be parsed correctly by the jsonnet
snippet.

This commit will cause the jsonnet snippet parser to parse input of the
form `import 'param://foo` to `params.foo` as opposed to the previous
`${foo}`.

${foo} does not provide an easily accessible way to the params that are
exposed through the params.libsonnet file. Since parameters are being
exposed using a local 'params' variable, it makes sense for the jsonnet
snippet to parse `import param://foo as `params.foo` instead.

Expose the import path to environments/:env/params.libsonnet as an
ExtCode so that it is made accessible to component files during
expansion.

This commit will generate the `environments/<env>/params.libsonnet` file
on `env add <env>`.

The purpose of this file is to allow users to define custom parameters
on an environment-to-environment basis. It is meant to allow for
"overrides" to component params.

The purpose of this file is to allow re-parameterization of components
after they are created.

`components/params.libsonnet` is generated on `ks init`. This file will
contain a jsonnet obj containing two objs:

1. global: contains user-defined global parameters; accessible to all
component and environments.
2. components: contains component-level parameters, defined initially
from `ks prototype use ...`

These objs are empty by default.

No need to redefine these flags as they are already specified in the
clientgo flag bindings.

'server' is consistent with what is used by clientgo. 'uri' only
introduces new language to ksonnet with the same meaning.

Support `diff`ing between two environments

Transition to pure Go implementation of Jsonnet

This change enables the user to diff between two environments that are
either local or remote.

i.e.,

`kubecfg diff local:dev local:prod` will diff between the expanded
templates for each environment on disk.

`kubecfg diff remote:dev remote:prod` will diff between two remote
environment clusters. It does this by first expanding the component
templates of each environment. Then, the live objects are fetched from
each of the clusters and the diff is performed against the live objects.

`kubecfg diff local:dev remote:prod` is also an option. This will diff
between the expanded templates for 'dev' on disk and the live objects
on 'prod's server.

 Set env namespace to default when namespace not provided

For now, client-go bindings will be removed from the diff command.

Doing this because when diffing between multiple remote environments, it
becomes ambiguous which environment cluster the flags should belong to.

`ks env set foo --namespace=""` and `ks env add foo` will both set the
namespace to 'default' in the environment's spec.json file.

 Init env metadata from provided context

`ks env add myenv --context=dev` will initialize the environment URI
and namespace based on the context `dev`, as specfied in the
kubeconfig file. The same applies for `ks init foo --context=dev`.

If both the context and uri argument is not provided, the current
context is used.

This change will also remove uri as a mandatory arg in `ks env add`.
The uri will be moved to a flag. It cannot be used at the same time as
`context`.

[docs] update readme

Signed-off-by: Jessica Yao <jessica@heptio.com>

Remove link to releases page

ksonnet.next isn't released yet. This message remained as a port from
the original README file in the kubecfg project.

Rename binary to 'ks';  rename 'kubecfg' references to 'ksonnet'

Introduce namespace to environments

Environments currently have the concept of a server URI, but it is
ambiguous which cluster namespace to use.

This commit will introduce the concept of namespaces to the env
commands.

For example,
`kubecfg env add staging http://mock-staging-uri \
 --namespace=staging-namespace`
`kubecfg env set staging --namespace=staging-namespace`

The default environment will use the namespace of the default context.

This commit will also update commands that take the <env> arg such as
`apply` to make use of the env namespace, if specified.

Environment base.libsonnet and overrides

Commands that take `env` as a param currently expand all files in the
`components` directory. This is no longer necessary with the
introduction of `base.libsonnet` and the per-environment override
`<env>.jsonnet` file.

This commit will simply expand the single `<env>.jsonnet` file (which
will implicitly expand all component files). The case of running
`ksonnet apply default`, is equivalent to running `ksonnet apply -f
environments/default/default.jsonnet`.

This commit will generate an "<env-name>.jsonnet" file when an
environment is created.

For example, the default environment would have the following tree
structure:
├── environments
│   ├── base.libsonnet
│   └── default
│       ├── .metadata
│       │   ├── k.libsonnet
│       │   ├── k8s.libsonnet
│       │   └── swagger.json
│       ├── default.jsonnet
│       └── spec.json

The goal of this file is to allow users to extend on base.libsonnet on a
per-environment basis to allow for custom overrides, such as replica
count.

base.libsonnet is a generated file that exists at the root of the
environments directory. This file is generated for all ksonnet projects.
The main goal of this file is to import all components in the components
directory, so that environments are able to easily extend / override any
one of these components in a modular structure.