Re: [PATCH] bash-completion: fix getting strategy list

> completion: find out supported merge strategies correctly
> 
> "git-merge" is a binary executable these days, and looking for assignment
> to $all_strategies variable does not work well.
> 
> When asked for an unknown strategy, pre-1.6.0 and post-1.6.0 "git merge"
> commands respectively say:
> 
>     $ $HOME/git-snap-v1.5.6.5/bin/git merge -s help
>     available strategies are: recur recursive octopus resolve stupid ours subtree 
>     $ $HOME/git-snap-v1.6.0/bin/git merge -s help
>     Could not find merge strategy 'help'.
>     Available strategies are: recursive octopus resolve ours subtree.
> 
> both on its standard error stream.  We can use this to learn what
> strategies are supported.
> 
> The sed script is written in such a way that it catches both old and new
> message styles ("Available" vs "available", and the full stop at the end).
> It also allows future versions of "git merge" to line-wrap the list of
> strategies, and add extra comments, like this:
> 
>     $ $HOME/git-snap-v1.6.1/bin/git merge -s help
>     Could not find merge strategy 'help'.
>     Available strategies are: blame recursive octopus resolve ours
>     subtree.
>     Also you have custom strategies: theirs
> 
>     Make sure you spell strategy names correctly.