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| <title>git-update-ref(1)</title> | |
| </head> | |
| <body> | |
| <div id="header"> | |
| <h1> | |
| git-update-ref(1) Manual Page | |
| </h1> | |
| <h2>NAME</h2> | |
| <div class="sectionbody"> | |
| <p>git-update-ref - | |
| Update the object name stored in a ref safely | |
| </p> | |
| </div> | |
| </div> | |
| <h2>SYNOPSIS</h2> | |
| <div class="sectionbody"> | |
| <p><em>git-update-ref</em> [-m <reason>] (-d <ref> <oldvalue> | [--no-deref] <ref> <newvalue> [<oldvalue>])</p> | |
| </div> | |
| <h2>DESCRIPTION</h2> | |
| <div class="sectionbody"> | |
| <p>Given two arguments, stores the <newvalue> in the <ref>, possibly | |
| dereferencing the symbolic refs. E.g. <tt>git-update-ref HEAD | |
| <newvalue></tt> updates the current branch head to the new object.</p> | |
| <p>Given three arguments, stores the <newvalue> in the <ref>, | |
| possibly dereferencing the symbolic refs, after verifying that | |
| the current value of the <ref> matches <oldvalue>. | |
| E.g. <tt>git-update-ref refs/heads/master <newvalue> <oldvalue></tt> | |
| updates the master branch head to <newvalue> only if its current | |
| value is <oldvalue>. You can specify 40 "0" or an empty string | |
| as <oldvalue> to make sure that the ref you are creating does | |
| not exist.</p> | |
| <p>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:".</p> | |
| <p>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 <strong>real</strong> 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).</p> | |
| <p>If --no-deref is given, <ref> itself is overwritten, rather than | |
| the result of following the symbolic pointers.</p> | |
| <p>In general, using</p> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><tt>git-update-ref HEAD "$head"</tt></pre> | |
| </div></div> | |
| <p>should be a _lot_ safer than doing</p> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><tt>echo "$head" > "$GIT_DIR/HEAD"</tt></pre> | |
| </div></div> | |
| <p>both from a symlink following standpoint <strong>and</strong> an error checking | |
| standpoint. The "refs/" rule for symlinks means that symlinks | |
| that point to "outside" the tree are safe: they'll be followed | |
| for reading but not for writing (so we'll never write through a | |
| ref symlink to some other tree, if you have copied a whole | |
| archive by creating a symlink tree).</p> | |
| <p>With <tt>-d</tt> flag, it deletes the named <ref> after verifying it | |
| still contains <oldvalue>.</p> | |
| </div> | |
| <h2>Logging Updates</h2> | |
| <div class="sectionbody"> | |
| <p>If config parameter "core.logAllRefUpdates" is true or the file | |
| "$GIT_DIR/logs/<ref>" exists then <tt>git-update-ref</tt> will append | |
| a line to the log file "$GIT_DIR/logs/<ref>" (dereferencing all | |
| symbolic refs before creating the log name) describing the change | |
| in ref value. Log lines are formatted as:</p> | |
| <ol> | |
| <li> | |
| <p> | |
| oldsha1 SP newsha1 SP committer LF | |
| </p> | |
| <p>Where "oldsha1" is the 40 character hexadecimal value previously | |
| stored in <ref>, "newsha1" is the 40 character hexadecimal value of | |
| <newvalue> and "committer" is the committer's name, email address | |
| and date in the standard GIT committer ident format.</p> | |
| </li> | |
| </ol> | |
| <p>Optionally with -m:</p> | |
| <ol> | |
| <li> | |
| <p> | |
| oldsha1 SP newsha1 SP committer TAB message LF | |
| </p> | |
| <p>Where all fields are as described above and "message" is the | |
| value supplied to the -m option.</p> | |
| </li> | |
| </ol> | |
| <p>An update will fail (without changing <ref>) 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.</p> | |
| </div> | |
| <h2>Author</h2> | |
| <div class="sectionbody"> | |
| <p>Written by Linus Torvalds <torvalds@osdl.org>.</p> | |
| </div> | |
| <h2>GIT</h2> | |
| <div class="sectionbody"> | |
| <p>Part of the <a href="git.html">git(7)</a> suite</p> | |
| </div> | |
| <div id="footer"> | |
| <div id="footer-text"> | |
| Last updated 19-Jul-2007 02:09:58 UTC | |
| </div> | |
| </div> | |
| </body> | |
| </html> |