mtimehash

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: https://github.com/golang/go/issues/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

Processing Files

Pass a list of files to modify via stdin:

find . -type f | mtimehash files

In my project I use:

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

to skip large files and .git directory

Processing Directories

Pass a list of directories to modify via stdin:

find . -type d | mtimehash dirs

The directory modification time is set based on a hash of the directory contents (file and subdirectory names), making it deterministic based on what files are present in the directory.

Note: It's recommended to process files first, then directories:

find . -type f | mtimehash files
find . -type d | mtimehash dirs

This ensures directories get updated mtimes based on the final state of their contents.