mtimehash

CLI to modify files mtime (modification data time) based on the hash of the file content. This makes it deterministic regardless of when the file was created or modified.

Installation

go install github.com/slsyy/mtimehash/cmd/mtimehash@latest

Rationale

go test uses mtimes to determine, if files opened during tests has changed and thus: tests need to be re-run. Unfortunately in a typical CI workflow modifications times are random as git does not preserve them. This makes caching for those tests ineffective, which slows down the test execution

More information here: golang/go#58571

The trick is to set mtime based on the file content hash. This way the mtime is deterministic regardless of when the repository was modified/clone, so a hit ratio should be much higher.

Usage

Pass a list of files to modify via stdin:

find . -type f | mtimehash

In my project I use:

find . -type f -size -10000k ! -path ./.git/\*\* | mtimehash

to skip large files and .git directory