150 lines
5.3 KiB
Plaintext
150 lines
5.3 KiB
Plaintext
git-update-ref(1)
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=================
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NAME
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----
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git-update-ref - Update the object name stored in a ref safely
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SYNOPSIS
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--------
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[verse]
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'git update-ref' [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] <ref> <newvalue> [<oldvalue>] | --stdin [-z])
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DESCRIPTION
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-----------
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Given two arguments, stores the <newvalue> in the <ref>, possibly
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dereferencing the symbolic refs. E.g. `git update-ref HEAD
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<newvalue>` updates the current branch head to the new object.
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Given three arguments, stores the <newvalue> in the <ref>,
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possibly dereferencing the symbolic refs, after verifying that
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the current value of the <ref> matches <oldvalue>.
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E.g. `git update-ref refs/heads/master <newvalue> <oldvalue>`
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updates the master branch head to <newvalue> only if its current
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value is <oldvalue>. You can specify 40 "0" or an empty string
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as <oldvalue> to make sure that the ref you are creating does
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not exist.
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It also allows a "ref" file to be a symbolic pointer to another
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ref file by starting with the four-byte header sequence of
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"ref:".
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More importantly, it allows the update of a ref file to follow
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these symbolic pointers, whether they are symlinks or these
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"regular file symbolic refs". It follows *real* symlinks only
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if they start with "refs/": otherwise it will just try to read
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them and update them as a regular file (i.e. it will allow the
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filesystem to follow them, but will overwrite such a symlink to
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somewhere else with a regular filename).
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If --no-deref is given, <ref> itself is overwritten, rather than
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the result of following the symbolic pointers.
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In general, using
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git update-ref HEAD "$head"
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should be a _lot_ safer than doing
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echo "$head" > "$GIT_DIR/HEAD"
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both from a symlink following standpoint *and* an error checking
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standpoint. The "refs/" rule for symlinks means that symlinks
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that point to "outside" the tree are safe: they'll be followed
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for reading but not for writing (so we'll never write through a
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ref symlink to some other tree, if you have copied a whole
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archive by creating a symlink tree).
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With `-d` flag, it deletes the named <ref> after verifying it
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still contains <oldvalue>.
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With `--stdin`, update-ref reads instructions from standard input and
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performs all modifications together. Specify commands of the form:
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update SP <ref> SP <newvalue> [SP <oldvalue>] LF
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create SP <ref> SP <newvalue> LF
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delete SP <ref> [SP <oldvalue>] LF
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verify SP <ref> [SP <oldvalue>] LF
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option SP <opt> LF
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Quote fields containing whitespace as if they were strings in C source
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code; i.e., surrounded by double-quotes and with backslash escapes.
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Use 40 "0" characters or the empty string to specify a zero value. To
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specify a missing value, omit the value and its preceding SP entirely.
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Alternatively, use `-z` to specify in NUL-terminated format, without
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quoting:
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update SP <ref> NUL <newvalue> NUL [<oldvalue>] NUL
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create SP <ref> NUL <newvalue> NUL
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delete SP <ref> NUL [<oldvalue>] NUL
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verify SP <ref> NUL [<oldvalue>] NUL
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option SP <opt> NUL
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In this format, use 40 "0" to specify a zero value, and use the empty
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string to specify a missing value.
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In either format, values can be specified in any form that Git
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recognizes as an object name. Commands in any other format or a
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repeated <ref> produce an error. Command meanings are:
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update::
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Set <ref> to <newvalue> after verifying <oldvalue>, if given.
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Specify a zero <newvalue> to ensure the ref does not exist
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after the update and/or a zero <oldvalue> to make sure the
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ref does not exist before the update.
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create::
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Create <ref> with <newvalue> after verifying it does not
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exist. The given <newvalue> may not be zero.
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delete::
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Delete <ref> after verifying it exists with <oldvalue>, if
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given. If given, <oldvalue> may not be zero.
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verify::
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Verify <ref> against <oldvalue> but do not change it. If
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<oldvalue> zero or missing, the ref must not exist.
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option::
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Modify behavior of the next command naming a <ref>.
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The only valid option is `no-deref` to avoid dereferencing
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a symbolic ref.
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If all <ref>s can be locked with matching <oldvalue>s
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simultaneously, all modifications are performed. Otherwise, no
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modifications are performed. Note that while each individual
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<ref> is updated or deleted atomically, a concurrent reader may
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still see a subset of the modifications.
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Logging Updates
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---------------
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If config parameter "core.logAllRefUpdates" is true and the ref is one under
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"refs/heads/", "refs/remotes/", "refs/notes/", or the symbolic ref HEAD; or
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the file "$GIT_DIR/logs/<ref>" exists then `git update-ref` will append
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a line to the log file "$GIT_DIR/logs/<ref>" (dereferencing all
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symbolic refs before creating the log name) describing the change
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in ref value. Log lines are formatted as:
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. oldsha1 SP newsha1 SP committer LF
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+
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Where "oldsha1" is the 40 character hexadecimal value previously
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stored in <ref>, "newsha1" is the 40 character hexadecimal value of
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<newvalue> and "committer" is the committer's name, email address
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and date in the standard Git committer ident format.
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Optionally with -m:
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. oldsha1 SP newsha1 SP committer TAB message LF
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+
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Where all fields are as described above and "message" is the
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value supplied to the -m option.
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An update will fail (without changing <ref>) if the current user is
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unable to create a new log file, append to the existing log file
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or does not have committer information available.
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GIT
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---
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Part of the linkgit:git[1] suite
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