How to Clear Git Local Cache: An In-Depth Guide for Developers

As a developer, you likely use Git daily to version control your code. Over time, the Git local cache can build up with unwanted files and bloat your repository. Clearing out this cache helps optimize Git performance and save disk space.

In this comprehensive guide, we’ll cover:

• What the Git local cache is and why clearing it matters
• Step-by-step instructions for clearing cached files and the entire local cache
• Additional tips for managing your local Git cache
• Common causes of Git cache bloat
• Optimizing performance with cache clearing
• Best practices for Git cache management
• Commands for checking Git cache size
• Related data storage concepts in Git
• Cache growth benchmarks
• Recommended cache size limits
• Advanced configuration of cache pruning

What is the Git Local Cache?

The Git local cache lives in the .git directory inside each Git repository on your local machine.

Whenever you add new files and commit snapshots, Git stores copies of those files in this local cache. This allows you to revert changes, track history, and work offline without a remote connection.

Here are a few key things to know about the Git local cache:

• It can grow quickly as you add images, binaries, and other large files
• Cached files remain even if you delete them from your working tree
• By default, it does not have a size limit and will occupy all available disk space

Over time, this added bulk hurts Git performance. Clearing non-essential items from the cache is an easy optimization.

Why Clear the Git Local Cache?

Some key reasons for clearing cached files include:

Speed up Git operations: Lookup, commit, and checkout processes get slower as the cache grows. Compacting it improves speed.

Shrink repository size: Removing unwanted snapshots, binaries, etc. radically shrinks the repo. This saves local and remote space.

Remove unwanted files: Source files you delete from your working tree still linger in the cache. Pruning removes them fully.

Resolve issues: A corrupted or oversized cache can cause odd Git issues. Refreshing it fixes problems.

For all these reasons, periodically clearing cache clutter keeps Git lean and fast.

Common Causes of Git Cache Bloat

In most projects, these issues tend to bulk up the local Git cache over time:

• Large binary assets like videos, datasets, or images
• Machine-generated logs and temporary files
• Huge dependency folders like node_modules
• Stale build artifacts (.OBJ, .EXE files)
• Old commits with large files that got removed later

Unpruned, these files get snapshotted to the cache repeatedly, accumulating over weeks and months.

Here is a real-world example of size growth in a two person project over 1 year:

Note the hockey stick growth pattern as compression lagged further and further behind raw data. This tanked checkout and commit speeds.

Clearing Cache to Optimize Performance

By purging unused files from the cache, developers aim to:

• Speed up commits: Each commit snapshots the index state to the local cache. Less bloat makes this faster.
• Make checkouts near-instant: Transitioning between branches or commits requires extracting cached snapshots. A compact cache helps achieve the holy grail of sub-second checkouts.
• Shrink clone time: For new team members, cloning needs to transfer the cached repo history. A minimal, optimized cache helps cloning go faster.
• Reduce storage needs: Development teams balance per-user storage costs against repository size. Clearing bloat saves money on storage.

In concrete terms, here is an example of the performance gain after cache cleaning:

Metric	Before Cleanup	After Cleanup	Savings
Repo Size	3 GB	400 MB	87% smaller
git clone Time	2 min 10 sec	35 sec	83% faster
git commit Time	25 sec	5 sec	80% faster

These savings multiply across a full team to reclaim tremendous amounts of wasted productivity from cache bloat.

Best Practices for Git Cache Management

Follow these guidelines for keeping cache size reasonable long-term:

• Set size limits: Configure gc.sizeLimit to cap scaling. Recommend keeping under 3GB globally.
• Store asset binaries elsewhere: Images, videos and such cause extreme bloat. Use cloud storage instead of git adding them.
• Automate cache clearing: Set up CI cron jobs to nightly clear stale cache files using the methods below.
• Use .gitignore extensively: Temp files and machine-generated logs should never enter the cache. Aggressively ignore them.
• Commit smaller changes more often: Big code diffs + long intervals between commits = more bloat.
• Review existing cache contents: Periodically run git gc --auto and examine the output list of cached files to look for cleanup targets.

Checking Git Cache Size

To view current cache size info, use:

git count-objects -v

This displays:

count: 30
size: 100240
in-pack: 297076
packs: 2
size-pack: 5498
prune-packable: 0
garbage: 0
size-garbage: 0

Key details are:

• size: Total size of loose objects in KB
• in-pack: Total size of packed objects in KB
• packs: Number of packfiles
• size-pack: Size of packfiles

So in the above case, the cache is using ~100MB currently.

You can also directly view cache folder sizes:

du -sh .git/objects/

Related Concepts: Packfiles, GC, Reflogs

Some other relevant data concepts within Git:

Packfiles: Packed, compressed objects created by git gc. This combines loose objects to save space.

Garbage collection: git gc compresses loose objects into packfiles per above. It also prunes unreferenced objects.

Reflog: Transaction journal recording branch tip changes for X days to allow undestructive undoing. These are finally purged by git gc once too old per the reflog expiration policy.

So in summary:

• Packfiles store useful current data compressed and deduplicated
• GC creates packfiles + deletes useless objects
• Reflogs track recent actions for reliability

Cache clearing focuses only on removing packfile bulk – not undo safety nets or precious compressed objects.

Cache Growth Benchmarks

As a final benchmark, check typical Git cache sizes for different repository categories:

Repository Type	Typical Range	Bad Practice Range
Individual developers	50 MB – 500 MB	500 MB – 5 GB
Startups	500 MB – 5 GB	5 GB – 50 GB
Open source projects	1 GB – 15 GB	15 GB – 150 GB
Enterprises	5 GB – 100 GB	100 GB – 1 TB

Cache sizes above the higher thresholds there can severely inhibit developer speed and scaling capabilities.

Recommended Cache Size Limits

Given the data above, these limits keep most repositories running well while sustaining essential history:

Team Size	Recommended Cache Limit
Individuals	1 GB
Startups	5 GB
Enterprises	50 GB

Set gc.sizeLimit appropriately.

Additionally, employ cloud storage for assets driving oversized caching rather than blow out these limits.

Advanced Cache Pruning Configuration

For advanced teams, Git allows configuring automatic cache clearing by combining:

• gc.auto
• gc.autoPrune
• gc.pruneExpire

For example:

git config gc.auto 1
git config gc.autoPrune true
git config gc.pruneExpire 3.days.ago

Here we make 3 changes:

1. gc.auto 1: Run automatic garbage collection on repository events
2. gc.autoPrune true: Actually prune loose objects during automatic GC
3. gc.pruneExpire 3.days.ago: Set branches older than 3 days as eligible for pruning when GC runs. This ensures we do not prune actively used branches.

Together, this gives automated, safe cache management.

Conclusion

Managing Git‘s local cache is key for high performance. Letting it bloat causes slower commits, checkouts, and clones as well as storage headaches.

Clearing cached files should be part of your cleanup regimen along with pruning branches and garbage collection. Used wisely, these tools keep your repository speedy at any scale of team or history length.