New feature for 1.26 (master), $(JUJU_HOME)/aliases

[Tim Penhey]

Hi folks,

I scratched a personal itch yesterday and added the ability for users to
specify their own aliases for juju commands.

There are two primary use cases that I was trying to address.

Firstly, the ability to specify default flags for commands:
  status = status --format=tabular

I could never remember the right environment variable to set to get
tabular by default.

The second was to allow quicker iteration around playing with new CLI
structure.  As most people are aware, the 2.0 CLI is going to be
somewhat different to the current one, and I thought it would be good to
provide a way in which we could "test drive" the new CLI with the
existing codebase without having to actually code anything.

The aliases files lives in JUJU_HOME, and is a simple text file. Each
non blank line that doesn't start with a '#' is considered to be an
alias. The format is expected to be:

<command> = <command> [<args>...]

So we can do things like:

# stat is like two whole letters shorter...
stat = status --format=tabular

# list tests
list-environments = system environments
list-users = user list

and so on.

Tim