git-symbolic-ref(1) [xfree86 man page]

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

NAME

       git-symbolic-ref - Read, modify and delete symbolic refs

SYNOPSIS

       git symbolic-ref [-m <reason>] <name> <ref>
       git symbolic-ref [-q] [--short] <name>
       git symbolic-ref --delete [-q] <name>

DESCRIPTION

       Given one argument, reads which branch head the given symbolic ref refers to and outputs its path, relative to the .git/ directory.
       Typically you would give HEAD as the <name> argument to see which branch your working tree is on.

       Given two arguments, creates or updates a symbolic ref <name> to point at the given branch <ref>.

       Given --delete and an additional argument, deletes the given symbolic ref.

       A symbolic ref is a regular file that stores a string that begins with ref: refs/. For example, your .git/HEAD is a regular file whose
       contents is ref: refs/heads/master.

OPTIONS

       -d, --delete
	   Delete the symbolic ref <name>.

       -q, --quiet
	   Do not issue an error message if the <name> is not a symbolic ref but a detached HEAD; instead exit with non-zero status silently.

       --short
	   When showing the value of <name> as a symbolic ref, try to shorten the value, e.g. from refs/heads/master to master.

       -m
	   Update the reflog for <name> with <reason>. This is valid only when creating or updating a symbolic ref.

NOTES

       In the past, .git/HEAD was a symbolic link pointing at refs/heads/master. When we wanted to switch to another branch, we did ln -sf
       refs/heads/newbranch .git/HEAD, and when we wanted to find out which branch we are on, we did readlink .git/HEAD. But symbolic links are
       not entirely portable, so they are now deprecated and symbolic refs (as described above) are used by default.

       git symbolic-ref will exit with status 0 if the contents of the symbolic ref were printed correctly, with status 1 if the requested name is
       not a symbolic ref, or 128 if another error occurs.

GIT

       Part of the git(1) suite

Git 2.17.1							    10/05/2018						       GIT-SYMBOLIC-REF(1)

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 <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 and the ref is one under "refs/heads/", "refs/remotes/", "refs/notes/", or the symbolic
       ref HEAD; 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:

	1. 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:

	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 <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 git(1) suite

Git 1.7.10.4							    11/24/2012							 GIT-UPDATE-REF(1)