git/Documentation/git-update-ref.txt
Jeff King 48bb914ed6 doc: drop author/documentation sections from most pages
The point of these sections is generally to:

  1. Give credit where it is due.

  2. Give the reader an idea of where to ask questions or
     file bug reports.

But they don't do a good job of either case. For (1), they
are out of date and incomplete. A much more accurate answer
can be gotten through shortlog or blame.  For (2), the
correct contact point is generally git@vger, and even if you
wanted to cc the contact point, the out-of-date and
incomplete fields mean you're likely sending to somebody
useless.

So let's drop the fields entirely from all manpages except
git(1) itself. We already point people to the mailing list
for bug reports there, and we can update the Authors section
to give credit to the major contributors and point to
shortlog and blame for more information.

Each page has a "This is part of git" footer, so people can
follow that to the main git manpage.
2011-03-11 10:59:16 -05:00

90 lines
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git-update-ref(1)
=================
NAME
----
git-update-ref - Update the object name stored in a ref safely
SYNOPSIS
--------
'git update-ref' [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] <ref> <newvalue> [<oldvalue>])
DESCRIPTION
-----------
Given two arguments, stores the <newvalue> in the <ref>, possibly
dereferencing the symbolic refs. E.g. `git update-ref HEAD
<newvalue>` updates the current branch head to the new object.
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. `git update-ref refs/heads/master <newvalue> <oldvalue>`
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.
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, <ref> 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" > "$GIT_DIR/HEAD"
both from a symlink following standpoint *and* an error checking
standpoint. The "refs/" rule for symlinks means that symlinks
that point to "outside" the tree are safe: they'll be followed
for reading but not for writing (so we'll never write through a
ref symlink to some other tree, if you have copied a whole
archive by creating a symlink tree).
With `-d` flag, it deletes the named <ref> after verifying it
still contains <oldvalue>.
Logging Updates
---------------
If config parameter "core.logAllRefUpdates" is true or the file
"$GIT_DIR/logs/<ref>" exists then `git update-ref` 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:
. oldsha1 SP newsha1 SP committer LF
+
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.
Optionally with -m:
. 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 <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.
GIT
---
Part of the linkgit:git[1] suite