stackage-update: Update your package index incrementally (requires git)

stackage-update

This package provides an executable, stackage-update, which provides the same functionality as cabal update (it updates your local package index). However, instead of downloading the entire package index as a compressed tarball over insecure HTTP, it uses git to incrementally update your package list, and downloads over secure HTTPS.

It has minimal Haskell library dependencies (all dependencies are shipped with GHC itself) and only requires that the git executable be available on the PATH. It builds on top of the all-cabal-files repository.

Advantages

Versus standard cabal update, using stackage-update gives the following advantages:

• Only downloads the deltas from the last time you updated your index, threby requiring significantly less bandwidth
• Downloads over a secure HTTPS connection instead of an insecure HTTP connection
• Note that the all-cabal-files repo is also updated from Hackage over a secure HTTPS connection

Usage

Install from Hackage as usual with:

cabal update
cabal install stackage-update

From then on, simply run stackage-update instead of cabal update.

Limitations

This currently has no respect for customized remote-repos in your ~/.cabal/config file. It assumes you have a remote-repo named hackage.haskell.org which should be populated from the all-cabal-files repo. If you have some kind of custom setup, this tool won't work for you. The vast majority of users tend to not modify their remote-repos, so stackage-update should work for most people most of the time.

GPG signature verification

Since version 0.1.1.0, stackage-update supports verifying the GPG signature. In order to do so, you pass in the --verify argument. You must first set up your GPG keychain to trust the relevant key, such as with the following commands:

$ gpg --recv-key --keyserver keyserver.ubuntu.com D6CF60FD
$ gpg --edit D6CF60FD
gpg> trust
Your decision? 3
gpg> quit

This is an example session, and not intended to be a guide to good GPG and cryptography practice. If you would like to verify this signing key properly via a web of trust, you can contact Michael Snoyman, who is already a signer for this key. The fingerprint is:

E595 AD42 14AF A6BB 1552  0B23 E40D 74D6 D6CF 60FD

Note: the GPG key may be updated in the future following standard key rotation policies. If you note that the key information listed here is out of date, please open an issue/send a pull request.

Hash downloads

When run with the --hashes command line argument, this tool instead downloads from the all-cabal-hashes repository, which contains additional information for verifying the accuracy of a tarball. While stackage-update does nothing with this extra information, other tools (like stackage-install) may do so.

Why stackage?

You may be wondering why this tool is called stackage-update, when in fact the functionality is useful outside of the Stackage project itself. The reason is that the naming allows it to play nicely with the other Stackage command line tooling. Concretely, that means that if you have stackage-cli installed, stackage-update works as a plugin. However, you can certainly use stackage-update on its own without any other tooling or dependencies on the Stackage project.

Future enhancements

• Detect modified remote-repos and warn the user

Some notes

Data is stored as a git-repository at app-directory retrieved by getAppUserDataDirectory, so for Unix it is $HOME/.stackage-update/all-cabal-files. This is convenient because you can cd there and use regular git tools to see what's new.