Fixed issue #4133: libgit2 returned: failed to parse revision specifier (ref ending...

[TortoiseGit.git] / doc / source / en / TortoiseGit / git_doc / git-update-ref.xml

<?xml version="1.0" encoding="UTF-8"?>\r
<!DOCTYPE sect2 SYSTEM "../../../dtd/dblite.dtd">\r
\r
<sect2 lang="en" id="git-update-ref(1)">\r
    <title>git-update-ref(1)</title>\r
    <date>2023-11-02</date>\r
<revhistory><revision><date>2023-11-02</date></revision></revhistory>\r
<indexterm>\r
<primary>git-update-ref(1)</primary>\r
</indexterm>\r
<simplesect id="git-update-ref(1)__name">\r
<title>NAME</title>\r
<simpara>git-update-ref - Update the object name stored in a ref safely</simpara>\r
</simplesect>\r
<simplesect id="git-update-ref(1)__synopsis">\r
<title>SYNOPSIS</title>\r
<blockquote>\r
<literallayout><emphasis>git update-ref</emphasis> [-m &lt;reason&gt;] [--no-deref] (-d &lt;ref&gt; [&lt;oldvalue&gt;] | [--create-reflog] &lt;ref&gt; &lt;newvalue&gt; [&lt;oldvalue&gt;] | --stdin [-z])</literallayout>\r
</blockquote>\r
</simplesect>\r
<simplesect id="git-update-ref(1)__description">\r
<title>DESCRIPTION</title>\r
<simpara>Given two arguments, stores the &lt;newvalue&gt; in the &lt;ref&gt;, possibly\r
dereferencing the symbolic refs.  E.g. <emphasis>git update-ref HEAD\r
&lt;newvalue&gt;</emphasis> updates the current branch head to the new object.</simpara>\r
<simpara>Given three arguments, stores the &lt;newvalue&gt; in the &lt;ref&gt;,\r
possibly dereferencing the symbolic refs, after verifying that\r
the current value of the &lt;ref&gt; matches &lt;oldvalue&gt;.\r
E.g. <emphasis>git update-ref refs/heads/master &lt;newvalue&gt; &lt;oldvalue&gt;</emphasis>\r
updates the master branch head to &lt;newvalue&gt; only if its current\r
value is &lt;oldvalue&gt;.  You can specify 40 "0" or an empty string\r
as &lt;oldvalue&gt; to make sure that the ref you are creating does\r
not exist.</simpara>\r
<simpara>It also allows a "ref" file to be a symbolic pointer to another\r
ref file by starting with the four-byte header sequence of\r
"ref:".</simpara>\r
<simpara>More importantly, it allows the update of a ref file to follow\r
these symbolic pointers, whether they are symlinks or these\r
"regular file symbolic refs".  It follows <emphasis role="strong">real</emphasis> symlinks only\r
if they start with "refs/": otherwise it will just try to read\r
them and update them as a regular file (i.e. it will allow the\r
filesystem to follow them, but will overwrite such a symlink to\r
somewhere else with a regular filename).</simpara>\r
<simpara>If --no-deref is given, &lt;ref&gt; itself is overwritten, rather than\r
the result of following the symbolic pointers.</simpara>\r
<simpara>In general, using</simpara>\r
<literallayout class="monospaced">git update-ref HEAD "$head"</literallayout>\r
<simpara>should be a <emphasis>lot</emphasis> safer than doing</simpara>\r
<literallayout class="monospaced">echo "$head" &gt; "$GIT_DIR/HEAD"</literallayout>\r
<simpara>both from a symlink following standpoint <emphasis role="strong">and</emphasis> an error checking\r
standpoint.  The "refs/" rule for symlinks means that symlinks\r
that point to "outside" the tree are safe: they'll be followed\r
for reading but not for writing (so we'll never write through a\r
ref symlink to some other tree, if you have copied a whole\r
archive by creating a symlink tree).</simpara>\r
<simpara>With <emphasis>-d</emphasis> flag, it deletes the named &lt;ref&gt; after verifying it\r
still contains &lt;oldvalue&gt;.</simpara>\r
<simpara>With <emphasis>--stdin</emphasis>, update-ref reads instructions from standard input and\r
performs all modifications together.  Specify commands of the form:</simpara>\r
<literallayout class="monospaced">update SP &lt;ref&gt; SP &lt;newvalue&gt; [SP &lt;oldvalue&gt;] LF\r
create SP &lt;ref&gt; SP &lt;newvalue&gt; LF\r
delete SP &lt;ref&gt; [SP &lt;oldvalue&gt;] LF\r
verify SP &lt;ref&gt; [SP &lt;oldvalue&gt;] LF\r
option SP &lt;opt&gt; LF\r
start LF\r
prepare LF\r
commit LF\r
abort LF</literallayout>\r
<simpara>With <emphasis>--create-reflog</emphasis>, update-ref will create a reflog for each ref\r
even if one would not ordinarily be created.</simpara>\r
<simpara>Quote fields containing whitespace as if they were strings in C source\r
code; i.e., surrounded by double-quotes and with backslash escapes.\r
Use 40 "0" characters or the empty string to specify a zero value.  To\r
specify a missing value, omit the value and its preceding SP entirely.</simpara>\r
<simpara>Alternatively, use <emphasis>-z</emphasis> to specify in NUL-terminated format, without\r
quoting:</simpara>\r
<literallayout class="monospaced">update SP &lt;ref&gt; NUL &lt;newvalue&gt; NUL [&lt;oldvalue&gt;] NUL\r
create SP &lt;ref&gt; NUL &lt;newvalue&gt; NUL\r
delete SP &lt;ref&gt; NUL [&lt;oldvalue&gt;] NUL\r
verify SP &lt;ref&gt; NUL [&lt;oldvalue&gt;] NUL\r
option SP &lt;opt&gt; NUL\r
start NUL\r
prepare NUL\r
commit NUL\r
abort NUL</literallayout>\r
<simpara>In this format, use 40 "0" to specify a zero value, and use the empty\r
string to specify a missing value.</simpara>\r
<simpara>In either format, values can be specified in any form that Git\r
recognizes as an object name.  Commands in any other format or a\r
repeated &lt;ref&gt; produce an error.  Command meanings are:</simpara>\r
<variablelist>\r
<varlistentry>\r
<term>\r
update\r
</term>\r
<listitem>\r
<simpara>\r
        Set &lt;ref&gt; to &lt;newvalue&gt; after verifying &lt;oldvalue&gt;, if given.\r
        Specify a zero &lt;newvalue&gt; to ensure the ref does not exist\r
        after the update and/or a zero &lt;oldvalue&gt; to make sure the\r
        ref does not exist before the update.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
create\r
</term>\r
<listitem>\r
<simpara>\r
        Create &lt;ref&gt; with &lt;newvalue&gt; after verifying it does not\r
        exist.  The given &lt;newvalue&gt; may not be zero.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
delete\r
</term>\r
<listitem>\r
<simpara>\r
        Delete &lt;ref&gt; after verifying it exists with &lt;oldvalue&gt;, if\r
        given.  If given, &lt;oldvalue&gt; may not be zero.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
verify\r
</term>\r
<listitem>\r
<simpara>\r
        Verify &lt;ref&gt; against &lt;oldvalue&gt; but do not change it.  If\r
        &lt;oldvalue&gt; is zero or missing, the ref must not exist.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
option\r
</term>\r
<listitem>\r
<simpara>\r
        Modify behavior of the next command naming a &lt;ref&gt;.\r
        The only valid option is <emphasis>no-deref</emphasis> to avoid dereferencing\r
        a symbolic ref.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
start\r
</term>\r
<listitem>\r
<simpara>\r
        Start a transaction. In contrast to a non-transactional session, a\r
        transaction will automatically abort if the session ends without an\r
        explicit commit. This command may create a new empty transaction when\r
        the current one has been committed or aborted already.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
prepare\r
</term>\r
<listitem>\r
<simpara>\r
        Prepare to commit the transaction. This will create lock files for all\r
        queued reference updates. If one reference could not be locked, the\r
        transaction will be aborted.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
commit\r
</term>\r
<listitem>\r
<simpara>\r
        Commit all reference updates queued for the transaction, ending the\r
        transaction.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
<varlistentry>\r
<term>\r
abort\r
</term>\r
<listitem>\r
<simpara>\r
        Abort the transaction, releasing all locks if the transaction is in\r
        prepared state.\r
</simpara>\r
</listitem>\r
</varlistentry>\r
</variablelist>\r
<simpara>If all &lt;ref&gt;s can be locked with matching &lt;oldvalue&gt;s\r
simultaneously, all modifications are performed.  Otherwise, no\r
modifications are performed.  Note that while each individual\r
&lt;ref&gt; is updated or deleted atomically, a concurrent reader may\r
still see a subset of the modifications.</simpara>\r
</simplesect>\r
<simplesect id="git-update-ref(1)__logging_updates">\r
<title>LOGGING UPDATES</title>\r
<simpara>If config parameter "core.logAllRefUpdates" is true and the ref is one\r
under "refs/heads/", "refs/remotes/", "refs/notes/", or a pseudoref\r
like HEAD or ORIG_HEAD; or the file "$GIT_DIR/logs/&lt;ref&gt;" exists then\r
<emphasis>git update-ref</emphasis> will append a line to the log file\r
"$GIT_DIR/logs/&lt;ref&gt;" (dereferencing all symbolic refs before creating\r
the log name) describing the change in ref value.  Log lines are\r
formatted as:</simpara>\r
<literallayout class="monospaced">oldsha1 SP newsha1 SP committer LF</literallayout>\r
<simpara>Where "oldsha1" is the 40 character hexadecimal value previously\r
stored in &lt;ref&gt;, "newsha1" is the 40 character hexadecimal value of\r
&lt;newvalue&gt; and "committer" is the committer's name, email address\r
and date in the standard Git committer ident format.</simpara>\r
<simpara>Optionally with -m:</simpara>\r
<literallayout class="monospaced">oldsha1 SP newsha1 SP committer TAB message LF</literallayout>\r
<simpara>Where all fields are as described above and "message" is the\r
value supplied to the -m option.</simpara>\r
<simpara>An update will fail (without changing &lt;ref&gt;) if the current user is\r
unable to create a new log file, append to the existing log file\r
or does not have committer information available.</simpara>\r
</simplesect>\r
<simplesect id="git-update-ref(1)__git">\r
<title>GIT</title>\r
<simpara>Part of the <xref linkend="git(1)" /> suite</simpara>\r
</simplesect>\r
</sect2>\r