# How can I tell if anything was fetched? 5 messages from 2012-10-11 to 2012-10-12. Participants: Phil Lawrence, Andreas Schwab, Enrico Weigelt, Johannes Sixt, Jeff King. Thread: https://gitlist.dev/t/31788 ## Phil Lawrence, 2012-10-11 16:25 Subject: How can I tell if anything was fetched? Message-ID: URL: https://gitlist.dev/e/CAFRB3XkueafikCvwzBb%2BWOAG_1mEkVg1Yt6%3DteOuVwYd2zWVOw%40mail.gmail.com ``` I have a cron job that regularly fetches into a bare repo. Currently, the job then pushes the repo to another remote, regardless of whether or not anything was actually fetched. That's a waste. What is the best way to know whether or not anything was received during the fetch? I don't want to be stuck trying to parse the answer out of STDOUT and STDERR... One approach might be to first generate a state-of-the-repo SHA1: # http://stackoverflow.com/a/7350019/834039 # http://git-scm.com/book/ch9-2.html { git rev-list --objects --all git rev-list --objects -g --no-walk --all git rev-list --objects --no-walk \ $(git fsck --unreachable | grep '^unreachable commit' | cut -d' ' -f3) } | sort | uniq | git hash-object -w --stdin I could then do the git fetch, generate another state-of-the-repo SHA1 and compare... Thoughts? -- Phil Lawrence ``` ## Andreas Schwab, 2012-10-11 16:45 Subject: Re: How can I tell if anything was fetched? Message-ID: URL: https://gitlist.dev/e/m28vbdkley.fsf%40igel.home In-Reply-To: ``` Phil Lawrence writes: > One approach might be to first generate a state-of-the-repo SHA1: > # http://stackoverflow.com/a/7350019/834039 > # http://git-scm.com/book/ch9-2.html > { > git rev-list --objects --all > git rev-list --objects -g --no-walk --all > git rev-list --objects --no-walk \ > $(git fsck --unreachable | > grep '^unreachable commit' | > cut -d' ' -f3) > } | sort | uniq | git hash-object -w --stdin I think you'd only need to record the state of all refs (eg. the output of `git for-each-ref') to reliably detect any changes. Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different." ``` ## Enrico Weigelt, 2012-10-11 18:29 Subject: Re: How can I tell if anything was fetched? Message-ID: <369f3feb-20e5-444f-b718-15d7dc8f2c61@zcs> URL: https://gitlist.dev/e/369f3feb-20e5-444f-b718-15d7dc8f2c61%40zcs In-Reply-To: ``` > I think you'd only need to record the state of all refs (eg. the > output > of `git for-each-ref') to reliably detect any changes. I would just record the output of `git ls-remote . | sort -u` somewhere and compare it next time (maybe you even wanna grep for the desired ref namespaces). cu -- Mit freundlichen Grüßen / Kind regards Enrico Weigelt VNC - Virtual Network Consult GmbH Head Of Development Pariser Platz 4a, D-10117 Berlin Tel.: +49 (30) 3464615-20 Fax: +49 (30) 3464615-59 enrico.weigelt@vnc.biz; www.vnc.de ``` ## Johannes Sixt, 2012-10-12 06:28 Subject: Re: How can I tell if anything was fetched? Message-ID: <5077B88E.5060303@viscovery.net> URL: https://gitlist.dev/e/5077B88E.5060303%40viscovery.net In-Reply-To: ``` Am 10/11/2012 18:25, schrieb Phil Lawrence: > What is the best way to know whether or not anything was received > during the fetch? I don't want to be stuck trying to parse the answer > out of STDOUT and STDERR... what="--all" # or "--remotes=the-remote" presha1s=$(git rev-parse $what) git fetch the-remote if test -z "$(git rev-list -1 $what --not $presha1s)" then echo nothing new fi Error checking is left as an exercise for the user ;) -- Hannes ``` ## Jeff King, 2012-10-12 07:47 Subject: Re: How can I tell if anything was fetched? Message-ID: <20121012074739.GD17026@sigill.intra.peff.net> URL: https://gitlist.dev/e/20121012074739.GD17026%40sigill.intra.peff.net In-Reply-To: ``` On Thu, Oct 11, 2012 at 06:45:09PM +0200, Andreas Schwab wrote: > Phil Lawrence writes: > > > One approach might be to first generate a state-of-the-repo SHA1: > > # http://stackoverflow.com/a/7350019/834039 > > # http://git-scm.com/book/ch9-2.html > > { > > git rev-list --objects --all > > git rev-list --objects -g --no-walk --all > > git rev-list --objects --no-walk \ > > $(git fsck --unreachable | > > grep '^unreachable commit' | > > cut -d' ' -f3) > > } | sort | uniq | git hash-object -w --stdin > > I think you'd only need to record the state of all refs (eg. the output > of `git for-each-ref') to reliably detect any changes. To clarify on the "only" in your sentence: it is not just that recording the ref changes is more efficient. But recording the object state is actively wrong. You might have fetched ref changes that do not introduce new objects (e.g., a rewind of history, or a branch deletion). The before-and-after ref state is both sufficient and necessary. I suspect you already realized that, Andreas, but I wanted to make sure it was clear to readers, including the OP. Checking ref state does suffer from potential race conditions with any other simultaneous updates. I don't think there is any reason we couldn't have "git fetch" produce a machine-readable output detailing what happened. We already have the same for "git push". I think it is simply the case that nobody has really wanted it so far. -Peff ```