reverting vs resetting

reverting vs resetting

[Mihamina Rakotomandimby]

Manao ahoana, Hello, Bonjour,

We put a gateway iptables script (SNAT, DNAT,...) under GIT.

Someone (Bob) made a mistake on it, but he did not know. That broke the
gateway.

Another one (Andy), did not try to undo Bob's mistake but tried (and
tried, and tried... always committing) to solve the problem. Andy made
about 50 commits.

When we decided to giveup, we decided to get back to the configuration
before Bob broke it. But it would be interesting to see Andy's history.

Reverting or resetting?

As far as I know: 
- Reverting Bob's commit will only cancel Bob's mistake but not Andy's
  tries to solve it.
- Resetting will forget the history.

Any suggestion?

Misaotra, Thanks, Merci.

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Re: reverting vs resetting

[Avery Pennarun]

On Fri, Feb 5, 2010 at 1:12 AM, Mihamina Rakotomandimby
<mihamina@gulfsat.mg> wrote:
> When we decided to giveup, we decided to get back to the configuration
> before Bob broke it. But it would be interesting to see Andy's history.
>
> Reverting or resetting?

Try this:

    git checkout HEAD~5 .
    git commit -m "reverted back to the version before this mess"

Replace HEAD~5 with the revision you want it to look like.  But don't
forget the "." in the checkout line!  All the magic is in there.  When
you specify a path ("."), git won't change the revision HEAD points
to, but it will change all the files and the index to the ones from
the specified version.  Then you can commit these files, producing
effectively a single commit that undoes a bunch of previous ones.

Have fun,

Avery

Re: reverting vs resetting

[Junio C Hamano]

Avery Pennarun <apenwarr@gmail.com> writes:

> On Fri, Feb 5, 2010 at 1:12 AM, Mihamina Rakotomandimby
> <mihamina@gulfsat.mg> wrote:
>> When we decided to giveup, we decided to get back to the configuration
>> before Bob broke it. But it would be interesting to see Andy's history.
>>
>> Reverting or resetting?
>
> Try this:
>
>     git checkout HEAD~5 .
>     git commit -m "reverted back to the version before this mess"

Caveat: if Andy added new paths while experimenting, the above won't
remove it.  You would need something like this instead:

	git read-tree -m -u HEAD~50
        git commit -m "reverted back to the version before this mess"

But this all assumes that the futile experiment is worth keeping.  I
highly doubt it.

I would recommend to do this:

	git branch andy_failed_experiment
        git reset --hard HEAD~50
	;# and perhaps revert Bob's change here as well

There is no sane reason to keep the failed experiment that added nothing
of value to the history leading to the tip of the 'master' branch.

I am using the word _value_ but keep in mind that value is relative to the
purpose you have in mind.  The purpose of the 'master' branch presumably
is to keep and to improve on a working configuration of the gateway box.
For that particular purpose, you have to admit that Andy's futzing around
didn't add anything of value in the result.  Hence, that shouldn't be kept
in its history.

Andy and other people may be able to learn from the failed experiment
later, so it is perfectly Ok to keep the series of random hacks in a
separate branch to study at their leisure.  The purpose of the branch is
different from that of the 'master': it is to serve as a catalog of
things/ideas that did _not_ work.

Re: reverting vs resetting

[Matthieu Moy]

Junio C Hamano <gitster@pobox.com> writes:

> 	git branch andy_failed_experiment
>         git reset --hard HEAD~50
> 	;# and perhaps revert Bob's change here as well

So would I, and to complement Junio's answer: keeping a failure
followed by a repair means this experiment will appear more or less
forever in the output of "git log", "git blame", will break "git
bisect" on that part of history, and so on. Putting it on a separate
branch avoids this, and keeps it in a safe place to show newcommers:
"see, here's what you should not do" ;-).

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Re: reverting vs resetting

[Mihamina Rakotomandimby]

> Matthieu Moy <Matthieu.Moy@grenoble-inp.fr> :
> So would I, and to complement Junio's answer

Thank you all.

-- 
       Architecte Informatique chez Blueline/Gulfsat:
    Administration Systeme, Recherche & Developpement
                +261 34 29 155 34 / +261 33 11 207 36