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Diffstat (limited to 'Documentation/git-update-ref.txt')
| -rw-r--r-- | Documentation/git-update-ref.txt | 133 |
1 files changed, 76 insertions, 57 deletions
diff --git a/Documentation/git-update-ref.txt b/Documentation/git-update-ref.txt index 48b6683071..8a4281cde9 100644 --- a/Documentation/git-update-ref.txt +++ b/Documentation/git-update-ref.txt @@ -8,63 +8,46 @@ git-update-ref - Update the object name stored in a ref safely SYNOPSIS -------- [verse] -'git update-ref' [-m <reason>] [--no-deref] (-d <ref> [<oldvalue>] | [--create-reflog] <ref> <newvalue> [<oldvalue>] | --stdin [-z]) +'git update-ref' [-m <reason>] [--no-deref] (-d <ref> [<old-oid>] | [--create-reflog] <ref> <new-oid> [<old-oid>] | --stdin [-z]) DESCRIPTION ----------- -Given two arguments, stores the <newvalue> in the <ref>, possibly +Given two arguments, stores the <new-oid> in the <ref>, possibly dereferencing the symbolic refs. E.g. `git update-ref HEAD -<newvalue>` updates the current branch head to the new object. +<new-oid>` updates the current branch head to the new object. -Given three arguments, stores the <newvalue> in the <ref>, +Given three arguments, stores the <new-oid> 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 +the current value of the <ref> matches <old-oid>. +E.g. `git update-ref refs/heads/master <new-oid> <old-oid>` +updates the master branch head to <new-oid> only if its current +value is <old-oid>. You can specify 40 "0" or an empty string +as <old-oid> 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). +The final arguments are object names; this command without any options +does not support updating a symbolic ref to point to another ref (see +linkgit:git-symbolic-ref[1]). But `git update-ref --stdin` does have +the `symref-*` commands so that regular refs and symbolic refs can be +committed in the same transaction. 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>. +With `-d`, it deletes the named <ref> after verifying that it +still contains <old-oid>. With `--stdin`, update-ref reads instructions from standard input and performs all modifications together. Specify commands of the form: - update SP <ref> SP <newvalue> [SP <oldvalue>] LF - create SP <ref> SP <newvalue> LF - delete SP <ref> [SP <oldvalue>] LF - verify SP <ref> [SP <oldvalue>] LF + update SP <ref> SP <new-oid> [SP <old-oid>] LF + create SP <ref> SP <new-oid> LF + delete SP <ref> [SP <old-oid>] LF + verify SP <ref> [SP <old-oid>] LF + symref-update SP <ref> SP <new-target> [SP (ref SP <old-target> | oid SP <old-oid>)] LF + symref-create SP <ref> SP <new-target> LF + symref-delete SP <ref> [SP <old-target>] LF + symref-verify SP <ref> [SP <old-target>] LF option SP <opt> LF start LF prepare LF @@ -82,10 +65,14 @@ specify a missing value, omit the value and its preceding SP entirely. Alternatively, use `-z` to specify in NUL-terminated format, without quoting: - update SP <ref> NUL <newvalue> NUL [<oldvalue>] NUL - create SP <ref> NUL <newvalue> NUL - delete SP <ref> NUL [<oldvalue>] NUL - verify SP <ref> NUL [<oldvalue>] NUL + update SP <ref> NUL <new-oid> NUL [<old-oid>] NUL + create SP <ref> NUL <new-oid> NUL + delete SP <ref> NUL [<old-oid>] NUL + verify SP <ref> NUL [<old-oid>] NUL + symref-update SP <ref> NUL <new-target> [NUL (ref NUL <old-target> | oid NUL <old-oid>)] NUL + symref-create SP <ref> NUL <new-target> NUL + symref-delete SP <ref> [NUL <old-target>] NUL + symref-verify SP <ref> [NUL <old-target>] NUL option SP <opt> NUL start NUL prepare NUL @@ -100,25 +87,42 @@ recognizes as an object name. Commands in any other format or a repeated <ref> produce an error. Command meanings are: update:: - Set <ref> to <newvalue> after verifying <oldvalue>, if given. - Specify a zero <newvalue> to ensure the ref does not exist - after the update and/or a zero <oldvalue> to make sure the + Set <ref> to <new-oid> after verifying <old-oid>, if given. + Specify a zero <new-oid> to ensure the ref does not exist + after the update and/or a zero <old-oid> to make sure the ref does not exist before the update. create:: - Create <ref> with <newvalue> after verifying it does not - exist. The given <newvalue> may not be zero. + Create <ref> with <new-oid> after verifying it does not + exist. The given <new-oid> may not be zero. delete:: - Delete <ref> after verifying it exists with <oldvalue>, if - given. If given, <oldvalue> may not be zero. + Delete <ref> after verifying it exists with <old-oid>, if + given. If given, <old-oid> may not be zero. + +symref-update:: + Set <ref> to <new-target> after verifying <old-target> or <old-oid>, + if given. Specify a zero <old-oid> to ensure that the ref does not + exist before the update. verify:: - Verify <ref> against <oldvalue> but do not change it. If - <oldvalue> is zero or missing, the ref must not exist. + Verify <ref> against <old-oid> but do not change it. If + <old-oid> is zero or missing, the ref must not exist. + +symref-create: + Create symbolic ref <ref> with <new-target> after verifying + it does not exist. + +symref-delete:: + Delete <ref> after verifying it exists with <old-target>, if given. + +symref-verify:: + Verify symbolic <ref> against <old-target> but do not change it. + If <old-target> is missing, the ref must not exist. Can only be + used in `no-deref` mode. option:: - Modify behavior of the next command naming a <ref>. + Modify the behavior of the next command naming a <ref>. The only valid option is `no-deref` to avoid dereferencing a symbolic ref. @@ -141,7 +145,7 @@ abort:: Abort the transaction, releasing all locks if the transaction is in prepared state. -If all <ref>s can be locked with matching <oldvalue>s +If all <ref>s can be locked with matching <old-oid>s simultaneously, all modifications are performed. Otherwise, no modifications are performed. Note that while each individual <ref> is updated or deleted atomically, a concurrent reader may @@ -161,7 +165,7 @@ formatted as: 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 +<new-oid> and "committer" is the committer's name, email address and date in the standard Git committer ident format. Optionally with -m: @@ -175,6 +179,21 @@ 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. +NOTES +----- + +Symbolic refs were initially implemented using symbolic links. This is +now deprecated since not all filesystems support symbolic links. + +This command 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). + +SEE ALSO +-------- +linkgit:git-symbolic-ref[1] + GIT --- Part of the linkgit:git[1] suite |