Re: git -- how to revert build to as-originally-cloned?

[John Lumby <johnlumby@hotmail.com>]

On 05/20/11 12:25, George Spelvin wrote:
> Er, no.  One "git merge" command produces (at most) one commit.
> It may be that the head of the branch you merged in was already
> a merge commit, but tha
>
> You may find "gitk" useful for for visualizing all of this.

I have tried gitk.    Can you or someone tell me what the colours of the 
nodes in the top left signifies?
Specifically,   a commit of mine (done since all the merging I've been 
asking about) shows as yellow,
whereas all the ones prior to that show as blue.   (I have not altered 
or changed the colour scheme so
it's whatever the default is)

>
> A merge *is* exactly one commit.  A "merge commit" is just a commit with
> more than one ancestor.  Now, that merge can *point to* lots of other
> commits, but it doesn't exactly "consist of" them.
>
>
>
> Now, what might have happened to you was a "fast forward" merge.

Yes!    actually in the output of the merge command (that I showed in my 
original posting) it said

Updating 72a8f97..1b1cb1f
Fast-forward



> If you have a history like this:
>
> o--o--o--a--b--c--d
>
> And you ask git to merge a and d together, the result will be simply d.
> Git, by default, avoids creating useless merges in such a case.  So if
> you merge in someone else's work, and you haven't done anything locally
> since their branch split off from your HEAD, the result will not include
> a merge commit at all.  (A NEW merge commit; they branch might include
> merge commits.)
>
> Since the top merges in your example are by Dave Miller (and not by you),
> it looks like that's what happened in this case.

Yes indeed,   thanks for explaining.
So what would be the correct way,  before doing my fast-forward merge,
to have made some kind of mark pointing at "a",  which I could then have 
used
to undo the fast-forward,  without having to calculate the number of 
commits in between?
(supposing my branch was not anchored at "a" but at some much earlier 
point)?

Cheers,    John Lumby