Original chapter reference: Chapter 54: Update Object Name in Reference. The command options and documentation recipes below are fully transcribed from Git Notes for Professionals.
Section 54.1: Update Object Name in Reference
Use
Update the object name which is stored in reference
SYNOPSIS
git update-ref [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] [--create-reflog] <ref>
<newvalue> [<oldvalue>] | --stdin [-z])General Syntax
1. Dereferencing the symbolic refs, update the current branch head to the new object.
git update-ref HEAD <newvalue>2. Stores the newvalue in ref, after verify that the current value of the ref matches oldvalue.
git update-ref refs/head/master <newvalue> <oldvalue>above syntax updates the master branch head to newvalue only if its current value is oldvalue.
Use -d flag to deletes the named <ref> after verifying it still contains <oldvalue>.
Use --create-reflog, update-ref will create a reflog for each ref even if one would not ordinarily be created.
Use -z flag to specify in NUL-terminated format, which has values like update, create, delete, verify.
Update
Set <ref> to <newvalue> after verifying <oldvalue>, if given. Specify a zero <newvalue> to ensure the ref does not exist after the update and/or a zero <oldvalue> to make sure the ref does not exist before the update.
Create
Create <ref> with <newvalue> after verifying it does not exist. The given <newvalue> may not be zero.
Delete
Delete <ref> after verifying it exists with <oldvalue>, if given. If given, <oldvalue> may not be zero.
Verify
Verify <ref> against <oldvalue> but do not change it. If <oldvalue> zero or missing, the ref must not exist.