packedrefs

Packedrefs refers to the data structure used by Git to store reference names and their corresponding object IDs in a compact, efficient format. In a Git repository, references (refs) such as branches, tags, and remote-tracking branches are normally represented by individual files under the .git/refs directory, each containing a SHA‑1 or SHA‑256 hash that identifies a commit or other object. As the number of refs grows, maintaining a large number of small files can become inefficient for both storage and performance. To address this, Git can pack many refs into a single file named packed‑refs located in the .git directory.

The packed‑refs file contains lines of the form “<hash> <refname>”, optionally preceded by a comment line beginning with a hash (“#”). Annotated tags are stored with a caret (^) line indicating the peeled tag target. When a ref is packed, its individual file may be removed, allowing Git to resolve the ref by reading the single packed‑refs file. Operations that create, delete, or rename refs typically update both the loose ref files and the packed‑refs file; however, Git prefers updating loose refs for recent changes and only repacks when the number of loose refs exceeds a configurable threshold.

Git commands such as `git pack-refs --all` or `git repack` trigger the packing process, consolidating all existing refs into packed‑refs. The packed‑refs file is considered read‑only during normal operation, and Git locks it when performing updates to avoid concurrent modification. Understanding packed‑refs is useful for repository maintenance, troubleshooting missing branches, and optimizing performance in large or heavily used Git repositories.