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93 lines
3.1 KiB
93 lines
3.1 KiB
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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'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" > "$GIT_DIR/HEAD" |
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both from a symlink following standpoint *and* an error checking |
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standpoint. The "refs/" rule for symlinks means that symlinks |
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that point to "outside" the tree are safe: they'll be followed |
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for reading but not for writing (so we'll never write through a |
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ref symlink to some other tree, if you have copied a whole |
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archive by creating a symlink tree). |
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With `-d` flag, it deletes the named <ref> after verifying it |
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still contains <oldvalue>. |
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Logging Updates |
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--------------- |
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If config parameter "core.logAllRefUpdates" is true or the file |
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"$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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Author |
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------ |
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Written by Linus Torvalds <torvalds@osdl.org>. |
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GIT |
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--- |
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Part of the linkgit:git[7] suite
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