Re: [1.8.0] Provide proper remote ref namespaces

3 messages, 3 authors, 2016-06-15 · open the first message on its own page

Re: [1.8.0] Provide proper remote ref namespaces

From: Junio C Hamano <hidden>
Date: 2016-06-15 22:50:33

Johan Herland [off-list ref] writes:
Yes, replicating existing behavior w/explicit refspecs would look like this:

  [remote "origin"]
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD
        fetch = +refs/heads/*:refs/remotes/origin/*
        fetch = ~refs/tags/*:refs/tags/*
While this is fine, I am not sure about the "HEAD" part.  Most of the
protocol do not convey which branch HEAD points at (instead "clone" has to
guess), which eventually needs to be fixed.  Incremental updates via
"fetch" does not touch "HEAD" at all by design; unlike the real branch
heads "remotes/origin/$branch" that are used to keep copies of what are at
the remote, "remotes/origin/HEAD" is meant to be used by the local
repository to designate which of the remote branch is considered the
primary branch from local repository owner's point of view, primarily so
that you can say "origin" locally to mean "origin/next" by setting the
symref origin/HEAD to point at it.  In that sense, the guess made by
"clone" is only used to give an initial value.
FTR, my new/proposed refspecs would look like this:

  [remote "origin"]
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD
        fetch = +refs/heads/*:refs/remotes/origin/heads*
        fetch = ~+refs/tags/*:refs/remotes/origin/tags/*
      ( fetch = +refs/notes/*:refs/remotes/origin/notes/* )
      ( fetch = +refs/replace/*:refs/remotes/origin/replace/* )
I think you meant "refs/remotes/origin/heads/*" (note the slash) on the
RHS of the branch refspecs.

How's that different from refs/*:refs/remotes/origin/* by the way?  Also
if you give tags a totally separate namespace, I don't see much reason to
still give it the "auto-follow" semantics.  It is far simpler to explain
if you just fetch all of them and be done with it, no?
Yes, to me it seems intuitive that when you specify <URL> (even if <URL> 
corresponds to an existing remote) you do NOT update remote-tracking refs, 
but if you use <remote>, you should ALWAYS update remote-tracking refs.
Others may disagree.
One argument for disagreement used to be that an explicit fetch of a
single branch was a deliberate way to avoid updating the tracking branch
before examining what has been changed (i.e. "git fetch origin master"
followed by "git log origin/master..FETCH_HEAD" and hopefully followed by
"git pull origin" or somesuch).  But that was before reflog was adopted as
a reliable safety measure, and I don't think people should rely on that
behaviour anymore.

I would actually make an even stronger point that people should not base
their workflow on keeping remote tracking refs deliberately stale, which
is exactly the "feature" was meant to be used for.  What has happened on
the other end has already happened whether you like it or not, and there
is no point in your locally pretending that it didn't happen.  If you
don't like the latest update there, you go talk to the party that control
the remote and rectify the situation with them.  It may involve pushing a
reverting or correcting commit over there, or in the worst case you simply
stop pulling from them, forking the project in effect at that point.
It may seem so, but in my experience it doesn't really work perfectly: Even 
if I fully control the repo I push to, I still want precise control over 
what I push there. Sometimes I may working on 'next' and 'master' in 
parallel, and I might have finished and tested some bugfixes on 'master', 
while I still have unfinished/untested stuff on 'next'.
Yes, I do this all the time and I often say "git push ko maint master" (ko
is my name for the k.org repo).  I however don't feel inconvenienced by it
precisely because when I make such a push, I _know_ that I want to push
only these two branches.  Saying "only these two branches" explicitly from
the command line, and seeing only these two branches go out, are very
assuring to me.  I usually try to be much more organized to make sure all
four integration branches satisfy certain preconditions before pushing,
and I say "git push ko" only after I make sure they do.

I consider it is a good UI design to force myself to type more when I am
doing something un(der)disciplined and to let me type less when I am
following a good project hygiene.

Re: [1.8.0] Provide proper remote ref namespaces

From: Johan Herland <hidden>
Date: 2016-06-15 22:50:33

On Monday 14 February 2011, Junio C Hamano wrote:
Johan Herland [off-list ref] writes:
quoted
Yes, replicating existing behavior w/explicit refspecs would look like: 
  [remote "origin"]
  
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD
        fetch = +refs/heads/*:refs/remotes/origin/*
        fetch = ~refs/tags/*:refs/tags/*
While this is fine, I am not sure about the "HEAD" part.  Most of the
protocol do not convey which branch HEAD points at (instead "clone" has
to guess), which eventually needs to be fixed.  Incremental updates via
"fetch" does not touch "HEAD" at all by design; unlike the real branch
heads "remotes/origin/$branch" that are used to keep copies of what are
at the remote, "remotes/origin/HEAD" is meant to be used by the local
repository to designate which of the remote branch is considered the
primary branch from local repository owner's point of view, primarily so
that you can say "origin" locally to mean "origin/next" by setting the
symref origin/HEAD to point at it.  In that sense, the guess made by
"clone" is only used to give an initial value.
Ah, ok. I've misunderstood the purpose of "remotes/origin/HEAD" then. Feel 
free to remove that refspec line from my proposal, and leave it as a 
special-purpose thing set up by clone (and maintained by the user 
thereafter).

Still (as I think was recently discussed in another thread), the existence 
of remotes/origin/HEAD _does_ cause problems if the origin remote also has a 
branch called "refs/heads/HEAD" (which would collide when fetched into the 
local repo).
quoted
FTR, my new/proposed refspecs would look like this:
  [remote "origin"]
  
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD
        fetch = +refs/heads/*:refs/remotes/origin/heads*
        fetch = ~+refs/tags/*:refs/remotes/origin/tags/*
      
      ( fetch = +refs/notes/*:refs/remotes/origin/notes/* )
      ( fetch = +refs/replace/*:refs/remotes/origin/replace/* )
I think you meant "refs/remotes/origin/heads/*" (note the slash) on the
RHS of the branch refspecs.
Indeed. Thanks for pointing out the typo.
How's that different from refs/*:refs/remotes/origin/* by the way?
It's not, except that "refs/*:refs/remotes/origin/*" would fetch a too-large 
superset. E.g. it would fetch "refs/remotes/third-party/heads/foo" into 
"refs/remotes/origin/remotes/third-party/heads/foo", which we probably don't 
want.
Also
if you give tags a totally separate namespace, I don't see much reason to
still give it the "auto-follow" semantics.  It is far simpler to explain
if you just fetch all of them and be done with it, no?
Agreed. Also, to quote Peff in http://thread.gmane.org/gmane.comp.version-
control.git/160503/focus=160726 :

"Now you could argue that auto-follow is not worth the effort. It is
somewhat confusing, and I can't think of a time when it ever actually
reduced the set of objects I was fetching (as opposed to just fetching
all tags). But maybe others have use cases where it matters."

So if nobody disagree, I would have no problem with dropping the leading "~" 
from the refspec, thus disabling auto-following (tracking all tags 
explicitly instead).
quoted
Yes, to me it seems intuitive that when you specify <URL> (even if
<URL> corresponds to an existing remote) you do NOT update
remote-tracking refs, but if you use <remote>, you should ALWAYS
update remote-tracking refs. Others may disagree.
One argument for disagreement used to be that an explicit fetch of a
single branch was a deliberate way to avoid updating the tracking branch
before examining what has been changed (i.e. "git fetch origin master"
followed by "git log origin/master..FETCH_HEAD" and hopefully followed by
"git pull origin" or somesuch).  But that was before reflog was adopted
as a reliable safety measure, and I don't think people should rely on
that behaviour anymore.

I would actually make an even stronger point that people should not base
their workflow on keeping remote tracking refs deliberately stale, which
is exactly the "feature" was meant to be used for.  What has happened on
the other end has already happened whether you like it or not, and there
is no point in your locally pretending that it didn't happen.  If you
don't like the latest update there, you go talk to the party that control
the remote and rectify the situation with them.  It may involve pushing a
reverting or correcting commit over there, or in the worst case you
simply stop pulling from them, forking the project in effect at that
point.
Agreed.
quoted
It may seem so, but in my experience it doesn't really work perfectly:
Even if I fully control the repo I push to, I still want precise
control over what I push there. Sometimes I may working on 'next' and
'master' in parallel, and I might have finished and tested some
bugfixes on 'master', while I still have unfinished/untested stuff on
'next'.
Yes, I do this all the time and I often say "git push ko maint master"
(ko is my name for the k.org repo).  I however don't feel inconvenienced
by it precisely because when I make such a push, I _know_ that I want to
push only these two branches.  Saying "only these two branches"
explicitly from the command line, and seeing only these two branches go
out, are very assuring to me.  I usually try to be much more organized
to make sure all four integration branches satisfy certain preconditions
before pushing, and I say "git push ko" only after I make sure they do.

I consider it is a good UI design to force myself to type more when I am
doing something un(der)disciplined and to let me type less when I am
following a good project hygiene.
I don't doubt that the current behavior works well for you (otherwise I 
expect you would have changed it). However, what I've seen at $dayjob is 
that more inexperienced users will often push right after committing, and at 
that time they're still very much in the "working-on-one-branch" state of 
mind (as opposed to the "administering-multiple-branches" state of mind), so 
when they follow up a "git commit" with a "git push" they're surprised (or 
worse: oblivious) to the fact that "git push" can push multiple branches.

I guess it comes down to whether you fundamentally consider "git push" 
something that pushes multiple _branches_, or something that pushes multiple 
_commits_. And for the latter of those groups push.default == "matching" is 
inherently more "dangerous" than for the former. (Granted, me telling 
everyone to use push.default == "tracking" probably doesn't help them in 
discovering "git push"'s ability to update multiple branches.)


Have fun! :)

...Johan

-- 
Johan Herland, [off-list ref]
www.herland.net

Re: [1.8.0] Provide proper remote ref namespaces

From: Jakub Narebski <hidden>
Date: 2016-06-15 22:50:33

On Mon, 14 Feb 2011, Johan Herland wrote:
On Monday 14 February 2011, Junio C Hamano wrote:
quoted
Johan Herland [off-list ref] writes:
quoted
quoted
Yes, replicating existing behavior w/explicit refspecs would look like: 
  [remote "origin"]
  
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD
Perhaps

              setHead = master

or something like that?
quoted
quoted
        fetch = +refs/heads/*:refs/remotes/origin/*
        fetch = ~refs/tags/*:refs/tags/*
While this is fine, I am not sure about the "HEAD" part.  Most of the
protocol do not convey which branch HEAD points at (instead "clone" has
to guess), which eventually needs to be fixed.
Right.
quoted
Incremental updates via 
"fetch" does not touch "HEAD" at all by design; unlike the real branch
heads "remotes/origin/$branch" that are used to keep copies of what are
at the remote, "remotes/origin/HEAD" is meant to be used by the local
repository to designate which of the remote branch is considered the
primary branch from local repository owner's point of view, primarily so
that you can say "origin" locally to mean "origin/next" by setting the
symref origin/HEAD to point at it.  In that sense, the guess made by
"clone" is only used to give an initial value.
Well, we have "git remote set-branch <remote> -a" to re-do this guessing
or checking, and update 'remotes/origin/HEAD'...
Ah, ok. I've misunderstood the purpose of "remotes/origin/HEAD" then. Feel 
free to remove that refspec line from my proposal, and leave it as a 
special-purpose thing set up by clone (and maintained by the user 
thereafter).
See above for my `remote.<remote>.setHead` proposal.
Still (as I think was recently discussed in another thread), the existence 
of remotes/origin/HEAD _does_ cause problems if the origin remote also has a 
branch called "refs/heads/HEAD" (which would collide when fetched into the 
local repo).
True, though... can't we consider having branch named 'HEAD' as insane?
quoted
quoted
FTR, my new/proposed refspecs would look like this:
  [remote "origin"]
  
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD
        fetch = +refs/heads/*:refs/remotes/origin/heads*
        fetch = ~+refs/tags/*:refs/remotes/origin/tags/*
      
      ( fetch = +refs/notes/*:refs/remotes/origin/notes/* )
      ( fetch = +refs/replace/*:refs/remotes/origin/replace/* )
I think you meant "refs/remotes/origin/heads/*" (note the slash) on the
RHS of the branch refspecs.
Indeed. Thanks for pointing out the typo.
quoted
How's that different from refs/*:refs/remotes/origin/* by the way?
It's not, except that "refs/*:refs/remotes/origin/*" would fetch a too-large 
superset. E.g. it would fetch "refs/remotes/third-party/heads/foo" into 
"refs/remotes/origin/remotes/third-party/heads/foo", which we probably don't 
want.
Note that it is not given that notes and replaces should be per-remote
like remote-tracking branches, and not autofollowed like tags.
quoted
Also
if you give tags a totally separate namespace, I don't see much reason to
still give it the "auto-follow" semantics.  It is far simpler to explain
if you just fetch all of them and be done with it, no?
Agreed. Also, to quote Peff in http://thread.gmane.org/gmane.comp.version-
control.git/160503/focus=160726 :

"Now you could argue that auto-follow is not worth the effort. It is
somewhat confusing, and I can't think of a time when it ever actually
reduced the set of objects I was fetching (as opposed to just fetching
all tags). But maybe others have use cases where it matters."

So if nobody disagree, I would have no problem with dropping the leading "~" 
from the refspec, thus disabling auto-following (tracking all tags 
explicitly instead).
Well, to make use of somewhat contrived example: with current auto-follow
fetching of tags, when somebody tracks e.g. only 'maint' branch, he/she
wouldn't get "*-rcN" tags he/she is not interested in.

Worth preserving?

[...] 
I don't doubt that the current behavior works well for you (otherwise I 
expect you would have changed it). However, what I've seen at $dayjob is 
that more inexperienced users will often push right after committing, and at 
that time they're still very much in the "working-on-one-branch" state of 
mind (as opposed to the "administering-multiple-branches" state of mind), so 
when they follow up a "git commit" with a "git push" they're surprised (or 
worse: oblivious) to the fact that "git push" can push multiple branches.

I guess it comes down to whether you fundamentally consider "git push" 
something that pushes multiple _branches_, or something that pushes multiple 
_commits_. And for the latter of those groups push.default == "matching" is 
inherently more "dangerous" than for the former. (Granted, me telling 
everyone to use push.default == "tracking" probably doesn't help them in 
discovering "git push"'s ability to update multiple branches.)
Another solution is to tech them "topic branch" workflow, i.e. to do new
work on new feature branch, and only when it is ready merge it into one
of published branches (i.e. those that have matching branch in remote 
repository they push to).

-- 
Jakub Narebski
Poland
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