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Ruqaiya Beguwala
Ruqaiya Beguwala

Posted on • Originally published at Medium

Day 21/30 - Git Update-Ref – Manually Update Branch References

#programming #git #productivity

Introduction

Git is a powerful version control system, and sometimes you need to manipulate references (branches, tags, etc.) directly. The git update-ref command allows you to manually update branch references, which can be useful in advanced Git workflows.

What is git update-ref?

In Git, a reference (or ref) is a pointer to a commit (like branches and tags). Normally, you update refs using commands like git checkout, git branch, or git reset.

However, git update-ref lets you manually change these references, giving you precise control.

How Git Stores References Internally

Git references are stored in two primary locations:

  • .git/refs/heads/ (for branches)
  • .git/refs/tags/ (for tags)

Each file contains a commit hash. For example, main branch's ref is stored at:

.git/refs/heads/main
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containing:

abc1234...
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What Happens When You Run git update-ref?

When you run:

git update-ref refs/heads/main abc1234
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Internal Process:

  1. Checks if the reference exists (creates if new, updates if existing)
  2. Validates the commit hash (fails if invalid)
  3. Atomic update:
    • Creates a temporary lock file (.git/refs/heads/main.lock)
    • Writes the new hash
    • Renames the file to replace the old ref (prevents corruption)
  4. Updates reflog (if -m is used) in .git/logs/refs/heads/main
  5. Handles symbolic refs (like HEAD) unless --no-deref is specified

Basic Syntax 

git update-ref <ref-name> <new-commit-hash>
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Use Cases

Now that we know how update-ref works, let's go through some practical use cases.

1. Safely Updating a Branch

Move main to a specific commit:

git update-ref refs/heads/main abc1234
git show-ref main  # Verify
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2. Recovering a Deleted Branch

Restore feature-x using its last known commit:

git update-ref refs/heads/feature-x abc1234
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3. Atomic Updates & Scripting

Force-update a branch (non-fast-forward) with reflog message:

git update-ref -m "Force reset" refs/heads/main 123abcd --no-deref
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What Does git show-ref Do?

  • Lists all references (branches, tags, and other refs) in your repository
  • Shows the commit hash each reference points to
  • Helps verify reference states and debug Git operations

Basic Usage 

git show-ref
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Sample output:

abc1234 refs/heads/main
def5678 refs/heads/develop
9012345 refs/tags/v1.0
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Use Cases

1. View All References 

git show-ref --heads     # Only show branches
git show-ref --tags      # Only show tags
git show-ref --heads --tags  # Both branches and tags
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2. Verify Branch Existence

Check if a branch exists:

git show-ref --verify refs/heads/feature-x
# Returns commit hash if exists, error otherwise
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3. Find All References to a Commit 

git show-ref --abbrev -d | grep abc1234
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Shows both regular and dereferenced (peeled) tags

4. Compare Local and Remote References 

git show-ref origin/main  # Remote branch
git show-ref main        # Local branch
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Conclusion

Using show-ref and update-ref is like wielding Git’s root access—immensely powerful but demanding precision and care. Always verify with show-ref before making changes with update-ref, and your repository operations will be both safe and effective.

Up Next in the Series: git log --graph --oneline --all – Visualize branch history

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