Dedent comments when adding them to merge messages

This means that if you have the following in your instruction sheet:

	merge my-new-feature

		Some commentary here...

Instead of the merge message being:

	Merge branch 'my-new-feature' into integration

	* branch my-new-feature:
	  commit 1
	  commit 2

		Some commentary here...

The merge message will now be:

	Merge branch 'my-new-feature' into integration

	* branch my-new-feature:
	  commit 1
	  commit 2

	Some commentary here...

Note the changed indentation on the commentary.

Signed-off-by: John Keeping <john@keeping.me.uk>
Improve the output from 'git integration --continue'

When continuing, it is not the case that the current operation has been
skipped, the branch has been merged with conflicts resolved.  Improve
the output message to better reflect this.

Signed-off-by: John Keeping <john@keeping.me.uk>
Add "--add=<branch>" action

This allows simple adding of branches and can take advantage of
tab-completion of branch names in the shell.

Signed-off-by: John Keeping <john@keeping.me.uk>
Merge branch 'dedent-commentary'

Remove the indentation from the commentary when writing it into a merge
message.

* dedent-commentary:
  Dedent comments when adding them to merge messages
Merge branch 'add-option'

Allow branches to be added to the instruction sheet without needing to
open it in an editor.

* add-option:
  Add "--add=<branch>" action
Merge branch 'improve-continue-output'

Clarify what has happened in the output when continuing after resolving
a conflict during integration.

* improve-continue-output:
  Improve the output from 'git integration --continue'