Git gc

An optional variable that defaults to 250. It controls how much time is spent in the delta compression phase of object packing when git gc is executed with the --aggressive option.

Optional variable that defaults to 50. It controls the depth of compression git-repack uses during a git gc --aggresive execution

Optional variable that defaults to "2 weeks ago". It sets how long a inaccessible object will be preserved before pruning

Optional variable that defaults to "3 months ago". It sets how long a stale working tree will be preserved before being deleted.

Behind the scenes git gc actually executes a bundle of other internal subcommands like git prune, git repack, git pack and git rerere. The high-level responsibility of these commands is to identify any Git objects that are outside the threshold levels set from the git gc configuration. Once identified, these objects are then compressed, or pruned accordingly.

Garbage collection is run automatically on several frequently used commands:

• git pull
• git merge
• git rebase
• git commit

The frequency in which git gc should be manually executed corresponds to the activity level of a repository. A repository with a single contributing developer will need to execute git gc far less often than a frequently-updated multi-user repository.

git gc is a parent command and git prune is a child. git gc will internally trigger git prune. git prune is used to remove Git objects that have been deemed inaccessible by the git gc configuration. Learn more about git prune.

git gc can be invoked with the --aggressive command line option. The --aggressive option causes git gc to spend more time on its optimization effort. This causes git gc to run slower but will save more disk space after its completion. The effects of --aggressive are persistent and only need to be run after a large volume of changes to a repository.

The git gc --auto command variant first checks if any housekeeping is required on the repo before executing. If it finds housekeeping is not needed it exits without doing any work. Some Git commands implicitly run git gc --auto after execution to clean up any loose objects they have created.

Before execution git gc --auto will check the git configuration for threshold values on loose objects and packing compression size. These values can be set with git config. If the repository surpasses any of the housekeeping thresholds git gc --auto will be executed.

You're probably already using git gc without noticing. As discussed in the best practices section, it is automatically invoked through frequently used commands. If you want to manually invoke it simply execute git gc and you should see an output indicating the work it has performed.