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If passed both --no-deref and --stdin, update-ref would error out with a general usage message that did not at all suggest these options were incompatible. The manpage for update-ref did suggest through its synopsis line that --no-deref and --stdin were incompatible, but it sadly also incorrectly suggested that -d and --no-deref were incompatible. So the help around the --no-deref option is buggy in a few ways. The --stdin option did provide a different mechanism for avoiding dereferencing symbolic-refs: adding a line reading option no-deref before every other directive in the input. (Technically, if the user wants to do the extra work of first determining which refs they want to update or delete are symbolic, then they only need to put the extra "option no-deref" lines before the updates of those refs. But in some cases, that's more work than just adding the "option no-deref" before every other directive.) It's easier to allow the user to just pass --no-deref along with --stdin in order to tell update-ref that the user doesn't want any symbolic ref to be dereferenced. It also makes the update-ref documentation simpler. Implement that, and update the documentation to match. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
153 lines
5.4 KiB
Plaintext
153 lines
5.4 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>] [--no-deref] (-d <ref> [<oldvalue>] | [--create-reflog] <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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With `--create-reflog`, update-ref will create a reflog for each ref
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even if one would not ordinarily be created.
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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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