GIT-UPDATE-REF(1) Git Manual GIT-UPDATE-REF(1)

NAME
       git-update-ref - Update the object name stored in a ref safely

SYNOPSIS
       git update-ref [-m ] (-d  [] | [no-deref]   [])


DESCRIPTION
       Given two arguments, stores the  in the , possibly
       dereferencing the symbolic refs. E.g. git update-ref HEAD 
       updates the current branch head to the new object.

       Given three arguments, stores the  in the , possibly
       dereferencing the symbolic refs, after verifying that the current value
       of the  matches . E.g. git update-ref refs/heads/master
         updates the master branch head to  only
       if its current value is . You can specify 40 "0" or an empty
       string as  to make sure that the ref you are creating does
       not exist.

       It also allows a "ref" file to be a symbolic pointer to another ref
       file by starting with the four-byte header sequence of "ref:".

       More importantly, it allows the update of a ref file to follow these
       symbolic pointers, whether they are symlinks or these "regular file
       symbolic refs". It follows real symlinks only if they start with
       "refs/": otherwise it will just try to read them and update them as a
       regular file (i.e. it will allow the filesystem to follow them, but
       will overwrite such a symlink to somewhere else with a regular
       filename).

       If no-deref is given,  itself is overwritten, rather than the
       result of following the symbolic pointers.

       In general, using

           git update-ref HEAD "$head"

       should be a lot safer than doing

           echo "$head" > "$GITDIR/HEAD"

       both from a symlink following standpoint and an error checking
       standpoint. The "refs/" rule for symlinks means that symlinks that
       point to "outside" the tree are safe: they’ll be followed for reading
       but not for writing (so we’ll never write through a ref symlink to some
       other tree, if you have copied a whole archive by creating a symlink
       tree).

       With -d flag, it deletes the named  after verifying it still
       contains .

LOGGING UPDATES
       If config parameter "core.logAllRefUpdates" is true and the ref is one
       under "refs/heads/", "refs/remotes/", "refs/notes/", or the symbolic
       ref HEAD; or the file "$GITDIR/logs/" exists then git update-ref
       will append a line to the log file "$GITDIR/logs/" (dereferencing
       all symbolic refs before creating the log name) describing the change
       in ref value. Log lines are formatted as:

        1. oldsha1 SP newsha1 SP committer LF

           Where "oldsha1" is the 40 character hexadecimal value previously
           stored in , "newsha1" is the 40 character hexadecimal value of
            and "committer" is the committer’s name, email address
           and date in the standard Git committer ident format.

       Optionally with -m:

        1. oldsha1 SP newsha1 SP committer TAB message LF

           Where all fields are as described above and "message" is the value
           supplied to the -m option.

       An update will fail (without changing ) if the current user is
       unable to create a new log file, append to the existing log file or
       does not have committer information available.

GIT
       Part of the git(1) suite



Git 1.8.3.1                       11/02/2018                 GIT-UPDATE-REF(1)