maltmill

Create and update Homebrew third party Formulae

Description

maltmill retrieves artifacts from GitHub Releases and creates or updates Homebrew Formulae. It automatically detects platform-specific archives (darwin/linux, amd64/arm64), calculates SHA256 digests, and generates the Formula file.

This is useful for maintaining your own tap repository (e.g. homebrew-tap) without manually writing or updating Formula files.

The name "maltmill" comes from the malt mill — the equipment used at the beginning of the beer brewing process to grind malt.

Synopsis

Create a new Formula

% maltmill new -w Songmu/maltmill

This creates maltmill.rb from the latest GitHub Release. You can also specify a tag explicitly:

% maltmill new -w Songmu/maltmill@v1.0.0

Use -o to specify the output file name:

% maltmill new -o Formula/maltmill.rb Songmu/maltmill

Update existing Formulae

% maltmill -w maltmill.rb

This fetches the latest release, updates the version, rewrites archive URLs, and recalculates SHA256 digests. Multiple formula files can be specified at once:

% maltmill -w Formula/*.rb

If the repository uses prefixed tags (e.g. my-product-v1.2.3), use --tag-prefix:

% maltmill -w --tag-prefix my-product-v my-product.rb

If --tag-prefix is omitted, maltmill selects the latest release from plain semver tags (e.g. v1.2.3 or 1.2.3).

If a release contains non-archive assets such as .rpm or .deb packages alongside .tar.gz / .zip archives, maltmill may pick the wrong file. Use -asset to narrow down which assets to consider:

% maltmill -w -asset '\.(tar\.gz|zip)$' my-tool.rb

The value is a Go regular expression matched against each asset filename.

Without -w, the updated formula is printed to stdout.

Install

homebrew

% brew install Songmu/tap/maltmill

using ghg

% ghg get Songmu/maltmill

using aqua

% aqua g -i Songmu/maltmill

go install (for using HEAD)

% go install github.com/Songmu/maltmill/cmd/maltmill@main

Built binaries are available on GitHub Releases. https://github.com/Songmu/maltmill/releases

GitHub Token

maltmill accesses the GitHub API. To avoid rate limits or access private repositories, set a GitHub token via the GITHUB_TOKEN environment variable or the -token flag. If neither is provided, maltmill falls back to the token configured in git config (via github.token or credential helpers).

Options

Flag	Description
-w	Write the result back to the source file instead of stdout
-token	GitHub API token (default: $GITHUB_TOKEN)
-tag-prefix	Tag prefix used to select releases (e.g. my-product-v)
-asset	Regexp pattern to select release assets by filename (e.g. \.tar\.gz$)

new subcommand options

Flag	Description
-w	Write the result to <name>.rb instead of stdout
-o	Specify the output file path
-token	GitHub API token (default: $GITHUB_TOKEN)
-tag-prefix	Tag prefix used to select releases
-asset	Regexp pattern to select release assets by filename

Author

Songmu