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Comment by bsza | Hacker News Reader

git fetch is basically just one string comparison if there are no new commits [0], I don’t think it’s as costly as you make it sound.

[0] https://stackoverflow.com/a/44476803

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Maybe, but Git has hooks. The author could deploy on push to do it only when needed, and immediately when relevant, rather than having to decide on a trade-off between immediacy and doing a lot of useless operations.

Obviously, this approach might not work for everyone, but I like to self-host my repos and use a git hook (post-receive) like this:

  #!/bin/sh
  BUILDDIR=/home/buildhook/.ib-build
  BUILD=`grep build |cut -d" " -f2`
  if [ -n "$BUILD" ]
  then
          touch $BUILDDIR/$BUILD
  fi

And then the buildhook user has a job that runs every minute by cron:

  #!/bin/sh
  BUILDDIR=/home/buildhook/.ib-build
  BUILD=`ls -t $BUILDDIR | head -1`
  if [ -n "$BUILD" ]
  then
          rm -f $BUILDDIR/$BUILD
          (
          echo Building $BUILD on builder...
          ssh builder time ./build $BUILD
          ) 2>&1 | mail -s "Building $BUILD on builder" build@example.com
  fi

For my use case, on this repo, pushing to a branch with the word "build" in its name will trigger a build of that commit, which builds and packages it into a dpkg, and the build server hosts a private apt repository so I can just `apt-get update; apt-get install blah` on all the servers.

An alternative strategy is pushing to a different repo on a build server, etc.

I guess that would have been fine if we didn't have alternatives (ie: callbacks). He is already running a web server, so he could listen through that for updates.

If he breaks the server, then a callback/webhook notification for the fix won't work either.

If you want to use a callback for this I'd recommend still polling periodically anyway.

Problem with self-hosting though, if his server breaks, so does the callbacks.

It might be a string comparison, but one of the strings usually comes from a remote server, which can be costly.

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