From 129056370abff1cc0d347b98fe88afc44a6cb8c0 Mon Sep 17 00:00:00 2001 From: Junio C Hamano Date: Tue, 4 Oct 2005 16:45:01 -0700 Subject: [PATCH] Add missing documentation. Signed-off-by: Junio C Hamano --- Documentation/git-symbolic-ref.txt | 52 +++++++++++++++++++++++++++ Documentation/git-update-ref.txt | 58 ++++++++++++++++++++++++++++++ 2 files changed, 110 insertions(+) create mode 100644 Documentation/git-symbolic-ref.txt create mode 100644 Documentation/git-update-ref.txt diff --git a/Documentation/git-symbolic-ref.txt b/Documentation/git-symbolic-ref.txt new file mode 100644 index 0000000000..a851ae24c4 --- /dev/null +++ b/Documentation/git-symbolic-ref.txt @@ -0,0 +1,52 @@ +git-symbolic-ref(1) +=================== + +NAME +---- +git-symbolic-ref - read and modify symbolic refs + +SYNOPSIS +-------- +'git-symbolic-ref' [] + +DESCRIPTION +----------- +Given one argument, reads which branch head the given symbolic +ref refers to and outputs its path, relative to the `.git/` +directory. Typically you would give `HEAD` as the +argument to see on which branch your working tree is on. + +Give two arguments, create or update a symbolic ref to +point at the given branch . + +Traditionally, `.git/HEAD` is a symlink pointing at +`refs/heads/master`. When we want to switch to another branch, +we did `ln -sf refs/heads/newbranch .git/HEAD`, and when we want +to find out which branch we are on, we did `readlink .git/HEAD`. +This was fine, and internally that is what still happens by +default, but on platforms that does not have working symlinks, +or that does not have the `readlink(1)` command, this was a bit +cumbersome. On some platforms, `ln -sf` does not even work as +advertised (horrors). + +A symbolic ref can be a regular file that stores a string that +begins with `ref: refs/`. For example, your `.git/HEAD` *can* +be a regular file whose contents is `ref: refs/heads/master`. +This can be used on a filesystem that does not support symbolic +links. Instead of doing `readlink .git/HEAD`, `git-symbolic-ref +HEAD` can be used to find out which branch we are on. To point +the HEAD to `newbranch`, instead of `ln -sf refs/heads/newbranch +.git/HEAD`, `git-symbolic-ref HEAD refs/heads/newbranch` can be +used. + +Currently, .git/HEAD uses a regular file symbolic ref on Cygwin, +and everywhere else it is implemented as a symlink. This can be +changed at compilation time. + +Author +------ +Written by Junio C Hamano + +GIT +--- +Part of the gitlink:git[7] suite diff --git a/Documentation/git-update-ref.txt b/Documentation/git-update-ref.txt new file mode 100644 index 0000000000..69715aa061 --- /dev/null +++ b/Documentation/git-update-ref.txt @@ -0,0 +1,58 @@ +git-update-ref(1) +================= + +NAME +---- +git-update-ref - update the object name stored in a ref safely + +SYNOPSIS +-------- +`git-update-ref` [] + +DESCRIPTION +----------- +Given two arguments, stores the in the , possibly +dereferencing the symbolic refs. E.g. `git-update-ref HEAD +` updates the current branch head to the new object. + +Given three arguments, stores the in the , +possibly dereferencing the symbolic refs, after verifying that +the current value of the matches . +E.g. `git-update-ref refs/heads/master ` +updates the master branch head to only if its current +value is . + +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). + +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). + +Author +------ +Written by Linus Torvalds . + +GIT +--- +Part of the gitlink:git[7] suite