Minor improvements to the example combo-layer config file:
* Add the recently added branch option to the optional options section
* Mention in comments that last_revision gets updated during "update"
* Tidy up some more grammar

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

Move all example configuration to the example config file, tidy up a few
long lines and fix some grammar.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

The "init" subcommand will now copy the current state of each component
repository into the combo layer repository, set last_revision for each
component, and then use "git add" to set up the initial commit (but will
not actually make the initial commit - that is left up to the user).
Also take the opportunity to bump the version number.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

This patch adds the script "combo-layer" to manipulate combo layer
repos. A combo layer repo is a repo containing multiple component
repos, e.g. oe-core, bitbake, BSP repos. The combo layer repo needs to
be updated by syncing with the component repo upstream. This script
is written to assist the combo layer handling.

The combo layer tool provides three functionalities:
- init: when the combo layer repo and component repo does not exist,
  init will "git init" the combo layer repo, and also "git clone" the
  component repos

- update: combo layer tool will pull the latest commit from component
  repo upstream, and apply the commits since last update commit to the
  combo repo. If the user specifies interactive mode(--interactive),
  they can edit the patch list to select which commits to apply.

- splitpatch: split the combo repo commit into separate patches per
  component repo, to facilitate upstream submission.

Combo layer tool uses a config file to define the component repo info.
Please check the combo-layer.conf.example for a detailed explanation
of the config file fields.

Signed-off-by: Yu Ke <ke.yu@intel.com>
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>