The 06/08/09, Junio C Hamano wrote:

quoted text
>  Documentation/git-push.txt |   75 ++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 75 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/git-push.txt b/Documentation/git-push.txt
> index 2653388..c1ae82d 100644
> --- a/Documentation/git-push.txt
> +++ b/Documentation/git-push.txt
> @@ -195,6 +195,81 @@ reason::
>  	refs, no explanation is needed. For a failed ref, the reason for
>  	failure is described.
>  
> +Note about fast-forwards
> +------------------------
> +
> +When an update changes a branch (or more in general, a ref) that used to
> +point at commit A to point at another commit B, it is called a
> +fast-forward update if and only if B is a descendant of A.
> +
> +In a fast-forward update from A to B, the set of commits that the original
> +commit A built on top of is a subset of the commits the new commit B
> +builds on top of.  Hence, it does not lose any history.
> +
> +In contrast, a non-fast-forward update will lose history.

I believe that this sentence a bit too much scaring for the beginner.
There are two kinds of update (push and pull). We loose history only
when pushing. I know this applies to Documentation/git-push.txt but out
of this context (and because we talk about pull near from here), I think
it would be clearer to say something like:

	In contrast, a non-fast-forward push will loose history.

quoted text
>                                                             For example,
> +suppose you and somebody else started at the same commit X, and you built
> +a history leading to commit B while the other person built a history
> +leading to commit A.  The history looks like this:
> +
> +----------------
> +
> +      B
> +     /
> + ---X---A
> +
> +----------------

<...>

quoted text
> +Alternatively, you can rebase your change between X and B on top of A,
> +with "git pull --rebase", and push the result back.  The rebase will
> +create a new commit D that builds the change between X and B on top of
> +A.
> +
> +----------------
> +
> +      B   D
> +     /   /
> + ---X---A
> +
> +----------------

Wouldn't "git pull --rebase" loose B? Shouldn't we have this

  ----------------
  
            D
           /
   ---X---A
  
  ----------------

instead?

-- 
Nicolas Sebrecht
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