Haskell Stack .stack-work cache management helper

Motivation

Switching branches often triggers significant rebuilds. While this is not an issue for small projects, it gets quite frustrating for larger codebases with long build times (such as half an hour).

Solution

Have separate .stack-work per branch. We'd also like to reuse existing cache for new branches – we copy cache from master branch using Copy-on-Write strategy available on APFS (macOS) and some Linux filesystems (e.g. btrfs).

Note: We could not use --work-dir Stack flag, since changing this also triggers rebuilds – this prevents from copying cache between branches.

As a bonus, we also exclude stack cache from Time Machine backups.

Setup

1. Add stack-cache to $PATH

2. Perform stack-cache init from the directory with stack.yaml

3. Add post-checkout git hook to call stack-cache relink on branch change (with appropriate working directory)

4. Make sure to ignore stack-cache directories:

git config --global core.excludesfile ~/.gitignore
echo .stack-work-cache >> ~/.gitignore
echo .stack-work >> ~/.gitignore

5. Periodically run stack-cache clean-all to free some disk space