If you have a repository with many submodules, it’s easy to update them all at once.

For example: I have my vim dotfiles in a Git repository. Not only does this make it easier for me to keep my vim setup the same across multiple machines, but also lets me add other bundles as submodules which makes it easy to update the bundles and propagate changes.

Once in a while I go into the repository and run:

git submodule foreach 'git pull || :'

The foreach command evaluates a shell command in each of the submodules. In this case git pull. The || : (in bash this is ‘or true’) stops the foreach command from terminating because of a non-zero return from the shell command.

Or, you could avoid the zero return problem by echoing the return value:

git submodule foreach 'echo `git pull`'

This is just one use of foreach. Since I don’t actually develop the submodules, I can keep the repository tidy by running:

git submodule foreach 'echo `git gc --aggressive`'

Just a quick one.

Say you have a repository with many remotes. Don’t roll your eyes; it’s very likely if you have many collaborators, or if you’re tracking a popular open source project. To pull down all available changes at once try this:

git fetch --all

No surprise about what it does.

Of course, this is a fetch, not a pull, which is a combination of git fetch and git merge, so after this command, don’t expect that your branches have been magically updated. I’m not a big fan of pull; I much prefer to fetch all changes and then explicitly merge with a chosen branch. In my case this works because I don’t have many tracking branches, because I find I can work just as well with the remote branches directly.