git-update-ref

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 "$head" > "$GIT_DIR/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 or the file
       "$GIT_DIR/logs/" exists then git update-ref will append a line to
       the log file "$GIT_DIR/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.

AUTHOR
       Written by Linus Torvalds .

GIT
       Part of the git(1) suite

NOTES
        1. torvalds@osdl.org
           mailto:torvalds@osdl.org



Git 1.7.0.4                       12/03/2010                 GIT-UPDATE-REF(1)