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In the earlier days, we used to spell the name of the system as GIT, to simulate as if it were typeset with capital G and IT in small caps. Later we stopped doing so at around 1.6.5 days. Let's stop doing so throughout the documentation. The name to refer to the whole system (and the concept it embodies) is "Git"; the command end-users type is "git". And document this in the coding guideline. Signed-off-by: Thomas Ackermann <th.acker@arcor.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
91 lines
3.2 KiB
Text
91 lines
3.2 KiB
Text
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>])
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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" > "$GIT_DIR/HEAD"
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both from a symlink following standpoint *and* an error checking
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standpoint. The "refs/" rule for symlinks means that symlinks
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that point to "outside" the tree are safe: they'll be followed
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for reading but not for writing (so we'll never write through a
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ref symlink to some other tree, if you have copied a whole
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archive by creating a symlink tree).
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With `-d` flag, it deletes the named <ref> after verifying it
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still contains <oldvalue>.
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Logging Updates
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---------------
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If config parameter "core.logAllRefUpdates" is true and the ref is one under
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"refs/heads/", "refs/remotes/", "refs/notes/", or the symbolic ref HEAD; or
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the file "$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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