Git multi-pack index quick reference¶

Essential commands¶

Task	Command
Write multi-pack index	`git multi-pack-index write`
Write MIDX with reachability bitmaps	`git multi-pack-index write --bitmap`
Set preferred pack for bitmaps	`git multi-pack-index write --bitmap --preferred-pack=pack-<sha>.pack`
Verify MIDX integrity	`git multi-pack-index verify`
Batch repack small packs (e.g. under 64MB)	`git multi-pack-index repack --batch-size=64M`
Expire and delete redundant packs	`git multi-pack-index expire`
Geometric repack with MIDX generation	`git repack --geometric=2 -d --write-midx`
Check pack and MIDX status	`ls -lh .git/objects/pack/`

Recommended configuration¶

# Enable MIDX support (default in modern Git)
git config core.multiPackIndex true

# Write reverse indexes for fast pack lookups
git config pack.writeReverseIndex true

# Cache object hashes in bitmaps
git config pack.writeBitmapHashCache true

CI maintenance pipeline snippet¶

Add this step to your runner maintenance cron or pipeline cleanup stage:

#!/usr/bin/env bash
set -euo pipefail

# Compact small packs without rewriting large historical packs
git multi-pack-index repack --batch-size=128M

# Remove obsolete packfiles
git multi-pack-index expire

# Update MIDX and generate reachability bitmaps
git multi-pack-index write --bitmap

# Validate index against pack checksums
git multi-pack-index verify

Troubleshooting¶

Corruption detected during verification¶

If git multi-pack-index verify returns non-zero:

# Remove corrupted MIDX file
rm -f .git/objects/pack/multi-pack-index*

# Rebuild clean MIDX from existing packfiles
git multi-pack-index write --bitmap

Bitmaps not generating¶

If --bitmap outputs a warning or fails:

Ensure the repository has at least one packfile. Loose objects are not indexed in bitmaps.
Run git repack -d or git multi-pack-index repack --batch-size=0 to convert loose objects into packs first.
Re-run git multi-pack-index write --bitmap.