Useful tracking branches and auto merging

Useful tracking branches and auto merging

[Felipe Contreras]

Hi,

For some time now I've stopped using 'git pull', and used 'git fetch',
and now 'git remote update', however, this is still not ideal.

 Your branch is behind 'origin/master' by 17 commits, and can be fast-forwarded.

This message doesn't tell me _how_ I can 'fast-forward', I do 'git
merge origin/master' but if git already knows 'master' is tracking
'origin/master' why should I specify that? Perhaps 'git merge
--tracking'.

But, while we are on that, why not automatically merge the tracking
branches? Perhaps 'git remote update --auto-merge', configurable so I
can make auto-merge the default, and perhaps make it the default in
1.8. Also, maybe some people would like them to be auto merged only
when they can be fast-forwarded.

I believe this would make remote tracking branches much more useful.
What do you think?

Cheers

-- 
Felipe Contreras

Re: Useful tracking branches and auto merging

[Jonathan Nieder]

Felipe Contreras wrote:

>  Your branch is behind 'origin/master' by 17 commits, and can be fast-forwarded.
> 
> This message doesn't tell me _how_ I can 'fast-forward', I do 'git
> merge origin/master' but if git already knows 'master' is tracking
> 'origin/master' why should I specify that? Perhaps 'git merge
> --tracking'.

git merge @{u}

> But, while we are on that, why not automatically merge the tracking
> branches?

Maybe 'git pull --all' could be taught to eventually do this?  That
would be incompatible with its current behavior of fetching everything
and merging some random branch, but I don't think anyone is relying
on that.

Re: Useful tracking branches and auto merging

[Felipe Contreras]

On Mon, Oct 4, 2010 at 11:46 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
> Felipe Contreras wrote:
>>  Your branch is behind 'origin/master' by 17 commits, and can be fast-forwarded.
>>
>> This message doesn't tell me _how_ I can 'fast-forward', I do 'git
>> merge origin/master' but if git already knows 'master' is tracking
>> 'origin/master' why should I specify that? Perhaps 'git merge
>> --tracking'.
>
> git merge @{u}

Interesting, I don't find anything like that in the documentation.
Moreover, wouldn't it make sense to make 'git merge' = 'git merge
@{u}'?

>> But, while we are on that, why not automatically merge the tracking
>> branches?
>
> Maybe 'git pull --all' could be taught to eventually do this?  That
> would be incompatible with its current behavior of fetching everything
> and merging some random branch, but I don't think anyone is relying
> on that.

Maybe, I feel 'git pull' is for single branches or repos, whereas 'git
remote update' is pretty clear it's for all the repos, so if some
merging is to be done for all the repos, it should be some form of
'git remote', no?

-- 
Felipe Contreras

Re: Useful tracking branches and auto merging

[Jonathan Nieder]

Felipe Contreras wrote:
> On Mon, Oct 4, 2010 at 11:46 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:

>> git merge @{u}
>
> Interesting, I don't find anything like that in the documentation.

The @{upstream} notation is documented in gitrevisions(7).  But yes,
a more prominent mention (maybe some examples?) would be nice.

> Moreover, wouldn't it make sense to make 'git merge' = 'git merge
> @{u}'?

I think so, yes. :)

>> Maybe 'git pull --all' could be taught to eventually do this?  That
>> would be incompatible with its current behavior of fetching everything
>> and merging some random branch, but I don't think anyone is relying
>> on that.
>
> Maybe, I feel 'git pull' is for single branches or repos, whereas 'git
> remote update' is pretty clear it's for all the repos

If I remember correctly, the current status is:

 - 'git remote' is for adding, removing, and pruning remotes
 - 'git fetch <remote>' and 'git fetch --all' are for updating them, and
 - 'git remote update' is for backward compatibility.

Re: Useful tracking branches and auto merging

[Felipe Contreras]

On Mon, Oct 4, 2010 at 11:57 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
> Felipe Contreras wrote:
>> On Mon, Oct 4, 2010 at 11:46 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
>>> git merge @{u}
>>
>> Interesting, I don't find anything like that in the documentation.
>
> The @{upstream} notation is documented in gitrevisions(7).  But yes,
> a more prominent mention (maybe some examples?) would be nice.
>
>> Moreover, wouldn't it make sense to make 'git merge' = 'git merge
>> @{u}'?
>
> I think so, yes. :)

Great :)

> If I remember correctly, the current status is:
>
>  - 'git remote' is for adding, removing, and pruning remotes
>  - 'git fetch <remote>' and 'git fetch --all' are for updating them, and
>  - 'git remote update' is for backward compatibility.

Oh, I thought 'git remote update' was newer. If 'git fetch --all' is
supposed to be used instead, then I guess 'git pull --all' makes
sense, but personally I would like it to error out if the merge is not
fast-forward.

Cheers.

-- 
Felipe Contreras

Re: Useful tracking branches and auto merging

[Junio C Hamano]

Jonathan Nieder <jrnieder@gmail.com> writes:

> Maybe 'git pull --all' could be taught to eventually do this?  That
> would be incompatible with its current behavior of fetching everything
> and merging some random branch, but I don't think anyone is relying
> on that.

I vaguely recall that we had discussions to disable "git pull --all",
which most likely is a mistake?

Re: Useful tracking branches and auto merging

[Felipe Contreras]

On Tue, Oct 5, 2010 at 7:35 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Jonathan Nieder <jrnieder@gmail.com> writes:
>
>> Maybe 'git pull --all' could be taught to eventually do this?  That
>> would be incompatible with its current behavior of fetching everything
>> and merging some random branch, but I don't think anyone is relying
>> on that.
>
> I vaguely recall that we had discussions to disable "git pull --all",
> which most likely is a mistake?

I believe this use-case is valid:

 * The user wants *all* his remote tracking branches to point to the
latest branch head in all the repos in the case the can be
fast-forwarded, and in the case they can't, print an error and
continue with the rest.

Right now I would have to do 'git fetch --all' go to every remote
tracking branch, and do 'git merge @{upstream}'.

Do you have a better idea how to achieve that instead of 'git pull --all'?

-- 
Felipe Contreras

Re: Useful tracking branches and auto merging

[Junio C Hamano]

Felipe Contreras <felipe.contreras@gmail.com> writes:

> I believe this use-case is valid:
>
> * The user wants *all* his remote tracking branches to point to the
> latest branch head in all the repos in the case the can be
> fast-forwarded, and in the case they can't, print an error and
> continue with the rest.

I would not be so sure about the validity of that use case.

If your tracking branches are always trailing, never having any real work
of your own, there is no reason to have them locally, instead of checking
them out on demand.  So let's forget about that case.

When you are collaborating with somebody else, sharing a topic branch, and
you are behind because you were not working on it while the other parties
progressed the shared topic, it would be convenient if your local branch
is fast-forwarded before you start to work on it.  One possible solution
for that would be to teach "git pull" to fast-forward such backgrounded
tracking branches that are not checked out.  Another obvious alternative
is to teach "git checkout" tell you where you are, and even tell you that
you could fast-forward [*1*].

On the other hand, if you have forked a topic branch to build your new
nifty feature at some known point (e.g. immediately after the upstream
reached a new stable point), but you haven't done any real work on it, it
is doubtful that it is even a good idea to fast-forward it automatically
to begin with.  C.f.

   Message-ID: <AANLkTim85sH_2o=xCiDuoQrHq_7ZL96Y91xQMGxUP5Fy@mail.gmail.com>

   "The real problem is that maintainers often pick random - and not at
    all stable - points for their development to begin with. They just
    pick some random "this is where Linus -git tree is today", and do
    their development on top of that. THAT is the problem - they are
    unaware that there's some nasty bug in that version."

IOW, once I decided one point is a good place to fork a topic, created a
branch off of it, but didn't have a chance to do a real work on it yet, it
would be very irritating if "git pull" updated that branch only because I
do not have my own commit on it yet.

I see little sanity in doing this with any option whose name has "all"; it
largely depends on the workflow, and in a single repository, some branches
may want to get fast-forwarded automatically while others don't [*2*].


[Footnotes]

*1* It is plausible that you could go one step further and define
branch.frotz.autofastforward configuration variable to tell "git checkout"
to fast-forward in such a case, perhaps only when the working tree and the
index are clean.

*2* It also is plausible that the same branch.frotz.autofastforward
configuration variable can be noticed by "git pull".

Re: Useful tracking branches and auto merging

[Felipe Contreras]

On Tue, Oct 5, 2010 at 11:10 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Felipe Contreras <felipe.contreras@gmail.com> writes:
>
>> I believe this use-case is valid:
>>
>> * The user wants *all* his remote tracking branches to point to the
>> latest branch head in all the repos in the case the can be
>> fast-forwarded, and in the case they can't, print an error and
>> continue with the rest.
>
> I would not be so sure about the validity of that use case.
>
> If your tracking branches are always trailing, never having any real work
> of your own, there is no reason to have them locally, instead of checking
> them out on demand.  So let's forget about that case.

Don't be so quick. Typing 'master' is certain easier than
'origin/master', or 'stable' rather than 'linux-stable/master', or
'vj-feature-1' rather than 'whatever-repo-this-came-from/feature-1'.
The fact that you don't do it doesn't mean it's not a valid use-case.

> On the other hand, if you have forked a topic branch to build your new
> nifty feature at some known point (e.g. immediately after the upstream
> reached a new stable point), but you haven't done any real work on it, it
> is doubtful that it is even a good idea to fast-forward it automatically
> to begin with.  C.f.

Fortunately we have 'git checkout --no-track -b origin/foo'. Problem solved.

But rather, what I do is:
% git branch -t origin/foo
% git checkout -b nifty-feature foo

>   Message-ID: <AANLkTim85sH_2o=xCiDuoQrHq_7ZL96Y91xQMGxUP5Fy@mail.gmail.com>
>
>   "The real problem is that maintainers often pick random - and not at
>    all stable - points for their development to begin with. They just
>    pick some random "this is where Linus -git tree is today", and do
>    their development on top of that. THAT is the problem - they are
>    unaware that there's some nasty bug in that version."
>
> IOW, once I decided one point is a good place to fork a topic, created a
> branch off of it, but didn't have a chance to do a real work on it yet, it
> would be very irritating if "git pull" updated that branch only because I
> do not have my own commit on it yet.

Then either:
1) fork of a local branch
2) use --no-track
3) don't do 'git pull --all'

> I see little sanity in doing this with any option whose name has "all"; it
> largely depends on the workflow, and in a single repository, some branches
> may want to get fast-forwarded automatically while others don't [*2*].

I think if you are issuing 'git pull --all' you want your remote
tracking branches to fast forward if possible, if not, why are you
doing 'git pull --all'?

Cheers.

-- 
Felipe Contreras

Re: Useful tracking branches and auto merging

[Clemens Buchacher]

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On Mon, Oct 04, 2010 at 11:56:02PM +0300, Felipe Contreras wrote:
>
> Moreover, wouldn't it make sense to make 'git merge' = 'git merge
> @{u}'?

Isn't that what 'git pull' does? Especially after using 'git
fetch'?

I prefer 'git merge' as one of the few git commands without magic
behavior and DWIMery.

Clemens

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Re: Useful tracking branches and auto merging

[Felipe Contreras]

On Sun, Oct 10, 2010 at 8:15 PM, Clemens Buchacher <drizzd@aon.at> wrote:
> On Mon, Oct 04, 2010 at 11:56:02PM +0300, Felipe Contreras wrote:
>>
>> Moreover, wouldn't it make sense to make 'git merge' = 'git merge
>> @{u}'?
>
> Isn't that what 'git pull' does? Especially after using 'git
> fetch'?

No, it hits the network again: git pull = git fetch + git merge @{u}

If I already did 'git fetch' why should I do it again?

> I prefer 'git merge' as one of the few git commands without magic
> behavior and DWIMery.

There's no magic involved, it's just what you would expect, what else
should 'git merge' (without arguments) do?

-- 
Felipe Contreras

Re: Useful tracking branches and auto merging

[Clemens Buchacher]

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On Sun, Oct 10, 2010 at 08:30:22PM +0300, Felipe Contreras wrote:
> 
> There's no magic involved, it's just what you would expect, what else
> should 'git merge' (without arguments) do?

I would expect it to do nothing, or just output a usage. The
proposed behavior is also unexpected because git-pull already does
(almost) the same thing.

Clemens

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Re: Useful tracking branches and auto merging

[Felipe Contreras]

On Sun, Oct 10, 2010 at 8:45 PM, Clemens Buchacher <drizzd@aon.at> wrote:
> On Sun, Oct 10, 2010 at 08:30:22PM +0300, Felipe Contreras wrote:
>>
>> There's no magic involved, it's just what you would expect, what else
>> should 'git merge' (without arguments) do?
>
> I would expect it to do nothing, or just output a usage.

So you are not going to type this command, how can such change in
behavior affect you?

> The
> proposed behavior is also unexpected because git-pull already does
> (almost) the same thing.

Not true. By your logic 'git fetch' should also do nothing because
'git pull' does "the same thing".

-- 
Felipe Contreras