how to check remote git repo for updates without pull/fetch

how to check remote git repo for updates without pull/fetch

[Ivan Zorin]

Hello. I have not very hard question, but I don't know how to better do
it - could you tell me, please, does exist some way to check remote git
repository for updates without downloading any essential files? I
suppose, that such command should just type something like: "already
updated", if current working tree identical to remote repo, and
something like "there is some updates in remote repo", if remote repo
has some new commits and/or branches. Thanks.

Re: how to check remote git repo for updates without pull/fetch

[Shawn O. Pearce]

Ivan Zorin <ivan.a.zorin@gmail.com> wrote:
> Hello. I have not very hard question, but I don't know how to better do
> it - could you tell me, please, does exist some way to check remote git
> repository for updates without downloading any essential files? I
> suppose, that such command should just type something like: "already
> updated", if current working tree identical to remote repo, and
> something like "there is some updates in remote repo", if remote repo
> has some new commits and/or branches. Thanks.

There aren't any commands to do it.

What you could do is write a script based upon git ls-remote. A
really simple one might be:

	#!/bin/sh
	remote=$1
	o=.git/remote_cache.$remote
	n=$o.new$$
	git ls-remote $remote >$n
	if [ -f $o ]
	then
		if diff $o $n >/dev/null
		then
			echo "No changes"
		else
			mv $n $o
			echo "Updates available"
	else
		mv $n $o
		echo "New remote remembered..."
	fi

A much more complex one would actually rewrite refs/heads/ to
the correct refs/remotes/ namespace on your local repository and
compare the remote ref values to the local refs/remotes values.

Patches for git fetch --pretend or something might be interesting.
Though I recall a thread about this before on the MLand saying there
was no point.  Its not like you can see how big the download would
be until after its over.

-- 
Shawn.

Re: how to check remote git repo for updates without pull/fetch

[Ivan Zorin]

> does exist some way to check remote git repository for updates without downloading any essential files?
Well, actually, I think, that I've found one of possible soulution already:
First, check remote repo:
$ git ls-remote /path/to/git/repo
<some sha1-hash>	HEAD
...
Then check local repo:
$ cat .git/HEAD
ref: refs/heads/master
$ cat .git/refs/heads/master
<other sha1-hash>
So, if both hashes identical, then current working tree with HEAD, which points to "master", already up-to-dated,
but if they don't, then there is some updates at remote repo.

Re: how to check remote git repo for updates without pull/fetch

[James Cloos]

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Here is the script I use:


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#!/bin/bash
#
# does this git repo need a pull?
#
l=$(git log|head -1|awk '{print $NF}')
r=$(git ls-remote origin heads/master|awk '{print $1}')
test "${r}" != "${l}"


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-JimC 
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6

Re: how to check remote git repo for updates without pull/fetch

[David Aguilar]

2008/12/20 James Cloos <cloos@jhcloos.com>:
>
> #!/bin/bash
> #
> # does this git repo need a pull?
> #
> l=$(git log|head -1|awk '{print $NF}')
> r=$(git ls-remote origin heads/master|awk '{print $1}')
> test "${r}" != "${l}"
>
>
> -JimC
> --
> James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6
>
>

Hello

Your script will report false positives if you run that in a branch
where you've made local commits since git log's output will list a
commit that's not on the remote side.  Thus it'lll say 'you need to
pull' when really what happened was that you committed locally and the
sha1 test is no longer equal.  This is one of the reasons why it's a
good idea to always keep your local master clean.

There's two things you can do:

1. assume that you always keep your local 'master' branch clean.
That'll let you quickly compare your local master versus origin's
master:

#!/bin/sh
remotemaster=$(git ls-remote origin heads/master | awk '{print $1}')
localmaster=$(git rev-parse master)
test "$remotemaster" = "$localmaster"


2. You might have a local branch that's not called master but is
tracking origin/master.  Or, your master branch might not be clean.
You can accomodate that workflow with:

#!/bin/sh
remotemaster=$(git ls-remote origin heads/master | awk '{print $1}')
branchpoint=$(git merge-base origin/master HEAD)
test "$remotemaster" = "$branchpoint"


The difference is that we're checking against the branch point.  If
origin/master is beyond the branch point then chances are you need to
pull.



---- off topic, but related ----

BTW one sound recommendation that I've heard on this list is that your
topic branches should really be free of any unrelated changes.
Pulling stuff in "just because" changes the branch.  It's no longer
just "topic" -- it's now "topic" + whatever they happened to push
upstream.  That has some implications in that it makes it harder to
review what exactly went into the specific topic/feature since the
branch's history now contains unrelated changes.

An advantage of keeping your topic branches clean is that you can run:

    git diff $(git merge-base HEAD origin/master)

in your topic branch and you'll see *only* the changes that went into
that branch.  If you get into the habit of pulling stuff in then
you'll see your changes *and* stuff you've pulled in, which probably
has nothing to do with the original topic/feature, etc. etc.

Anyways, this is an entirely different topic/conversation and might
not apply to your specific circumstance but I figured I'd mention it
nonetheless.


-- 
    David

Re: how to check remote git repo for updates without pull/fetch

[Boyd Stephen Smith Jr.]

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On Saturday 2008 December 20 17:41:13 David Aguilar wrote:
> 2008/12/20 James Cloos <cloos@jhcloos.com>:
> > #!/bin/bash
> > #
> > # does this git repo need a pull?
> > #
> > l=$(git log|head -1|awk '{print $NF}')
> > r=$(git ls-remote origin heads/master|awk '{print $1}')
> > test "${r}" != "${l}"
> >
> >
> > -JimC
> > --
> > James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6
>
> Hello
>
> Your script will report false positives if you run that in a branch
> where you've made local commits since git log's output will list a
> commit that's not on the remote side.

Change the last line to:
test "${r}" != "$(git merge-base "${r}" "${l}")" and those false positives 
should go away.

The script is far from a complete solution to the OPs problem though.  It only 
checks one, specific remote branch.  It only checks against the current 
branch.  It is the core of something that might be useful as another 
subcommand to 'git remote' though.
-- 
Boyd Stephen Smith Jr.                     ,= ,-_-. =. 
bss@iguanasuicide.net                     ((_/)o o(\_))
ICQ: 514984 YM/AIM: DaTwinkDaddy           `-'(. .)`-' 
http://iguanasuicide.net/                      \_/     

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Re: how to check remote git repo for updates without pull/fetch

[James Cloos]

>>>>> "David" == David Aguilar <davvid@gmail.com> writes:

David> Your script will report false positives if you run that in a branch
David> where you've made local commits since git log's output will list a
David> commit that's not on the remote side.

Ah.  Yes.  I forgot to mention that.  Good catch.

I wrote the script specifically for use with the repos created by Gentoo's
git eclass (used when installing packages from git repos rather than from
tars or the like).  As such, it only needed to deal with pristine clones.

-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6