If you repeatedly clone a Git repository (for instance, for software you use to hack) you could annoyed by how long you have to wait for the clone operation, especially for large remote git repositories. On the other hand, if you have multiple copies of a Git repository on your computer, it can be a waste of space that you would prefer not to waste.

Git has a feature "--reference"/alternates, which allows you to reference commits from another local repo on the same computer.

An example use case is:

$ cd ~/test
$ git clone https://example.org/git/repo.git normal-repo
  (you wait minutes or hours, and the resulting directory is big)
$ git clone --reference ~/test/repo https://example.org/git/repo.git referenced-repo
  (you wait seconds, and the resulting directory is small - only the size of the files, no size used by the history)

Both clones can access the whole history of the Git repository. Internally, the second clone contains a file .git/objects/info/alternates containing the path of the first repo, which tells git to search the referenced alternates repo for any commits that can't be found in the current repo. Obviously, if you delete the referenced (first) repo, the second copy is useless and will display tonnes of errors. Newer versions of git have a '--dissociate' feature that allows the copy to be independent from the first.

git-cache creates a central cache directory on a computer, which contains most of the commits of regularly cloned Git repositories.

If you are a regular hacker of a software you can cache most commits and then only download the most recent ones.

Example use case:

$ sudo git cache init  # cache is located in /var/cache/git-cache
$ git cache add linux https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git

  You can now use the cache directory with:

      git cache clone linux

  Or clone a similiar fork:

      git cache clone git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git

Installation: Copy git-cache into your git commands directory (e.g. Ubuntu: /usr/lib/git-core) and make sure it is executable by all users (mode 0755).

Usage: All commands have the format:

git cache ACTION [SUB-ACTION] PARAMETERS

Commands:

# General maintenance commands
git cache init [DIR] [TYPE]         initialise the cache directory; TYPE=local|global (default: local)
git cache delete --force            delete the cache directory

# Daily commands
git cache add NAME URL                               add a cached git repository
git cache rm --force NAME                            remove a cached git repository
git cache show                                       show all cached git repositories
git cache update                                     fetch all cached git repository
git cache clone [--dependent] URL/NAME [DIR]         clone using cache
git cache submodule add [--dependent] URL/NAME [DIR] add submodule using cache

clone commands accept either the name of an already cached git repository or an arbitrary remote URL
cloning remote forks will still result in a signifigant speedup, any objects found in cache will be used rather than downloaded
--dependent will keep object alternate references to the cache, which results in less disk space, but the repository depends on the cache existence
without the option the clone will take up more space, but it will be independent like a normal clone

(Any other command will be applied to the cache directory.)
 e.g. 'git cache gc' or 'git cache remote show'.)

Location of the cache directory: The default cache directory contains all cached repositories (each Git repository is a remote). If it is created by the root user, the cache directory is /var/cache/git-cache, otherwise it is ~/.cache/git-cache; it can also be configured to use another directory if you specify this with the init command.

Note: This directory could become big, be sure you have enough space.

You may want to create a cron-job to run git cache update to automatically retrieve new commits. (bug)

• Original author: Seb35
• Licence: WTFPL 2.0

This program is a generalisation to arbitrary Git repositories of an idea and implementation by Randy Fay specifically for Drupal. Hopefully this generalisation is sufficiently simple to stay useable and practical.

Similar program: git-cached by dvessel