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I want to write a fast script that checks if a remote repo has changes compared to the local one, and then pull all the changes, for all the branches, if it does.

Is there a way to do this without actually pulling all the changes, first?

Everything I've seen around git remote update and such actually downoads stuff, etc. and it's slow for many repos.

Think of this as a sort of dry-run: run this script often for many repos and run another script to actually update the local repos based on the report of the first script.

oblio
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  • It's not really clear why you'd want to check for changes without pulling anything if the thing you're going to do if there are any changes is pull them. – jonrsharpe May 13 '20 at 13:49
  • Does this answer your question? [How to preview git-pull without doing fetch?](https://stackoverflow.com/questions/180272/how-to-preview-git-pull-without-doing-fetch) – jonrsharpe May 13 '20 at 13:49
  • @jonrsharpe The first thing it does is git fetch, which is still a full download :( Regarding the reason, it's because I'd want to be aware of changes in those many repos and sometimes the update would be manual, sometimes it won't be done now, sometimes it would be done through the second, heavy, script. In any case, the use case is valid, is it possible, I wonder? – oblio May 13 '20 at 13:51
  • What about `git ls-remote https://github.com/githubtraining/hellogitworld.git` This should only get the commit hashes list. – Robert May 13 '20 at 13:54
  • @Robert, git ls-remote seems to be what I was wishing for. If you add it as an answer I'll mark it as correct. Thanks – oblio May 13 '20 at 13:56

4 Answers4

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If you just want to see the list of changes of a remote repository without a comparison to a local repository you can use the ls-remote command of git:

git ls-remote https://github.com/githubtraining/hellogitworld.git

It displays the list of commit hashes of the remote repository starting with HEAD:

git ls-remote https://github.com/githubtraining/hellogitworld.git
ef7bebf8bdb1919d947afe46ab4b2fb4278039b3        HEAD
a9095e79eaafd9f11a9d12e5a1ae125fde81a5eb        refs/heads/bisect
26479b0b606bc322e0b53226e44f343614bf06b6        refs/heads/fbaddfiles
c975e0e9a00f5f902877b0830a52010691586266        refs/heads/fbmaster
e650f374002f860d56ecad63b6fab7387a607642        refs/heads/feature_division
57d0bf61e57cdacb309ebd1075257c6bd7e1da81        refs/heads/feature_division_polished
7c0ffa9d88616972bb84befbec40a2212478149e        refs/heads/feature_image
3c9306fcc7c41a88a37514a1f4c8d43459eaf966        refs/heads/feature_subtraction
818f033c4ae7f26b2b29e904942fa79a5ccaadd0        refs/heads/feature_subtraction_polished
....
Robert
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1

see this SO.

TLDR

git remote update
git status -uno

or 

git fetch --dry-run
Ryan.Bartsch
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Technically there is no way to only looking for changes without downloading them to your local copy, however, the closest command you will find is git fetch. Technically it downloads the changes from the remote repository but does not apply them to your working branches only updates the remote branches in your local reference.

More information here: https://git-scm.com/docs/git-fetch

Erick Guillen
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  • Ummm... technically, there is. I want to **know** that there are changes (which should be light weight), not to **get** the changes (which can mean a billion files downloaded over slow network connections). – oblio May 13 '20 at 14:00
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git fetch: is the command that tells your local git to retrieve the latest meta-data info from the original (yet doesn’t do any file transferring. It’s more like just checking to see if there are any changes available).

Once you do git fetch, you can check the status for the remote changes.

C:\D_Drive\Dev\BootApps\Persistence-Concepts>git status
On branch topic2
Your branch is behind 'origin/topic2' by 2 commits, and can be fast-forwarded.
  (use "git pull" to update your local branch)

Untracked files:
  (use "git add <file>..." to include in what will be committed)

At this stage, your local repo do not have the changes but it shows the remote has n no of changes. So you can see the changes made at the remote without pulling.

Abdul
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