Symbolic refs are understood by resolve_ref(), so existing read_ref()
users will automatically understand them as well.
Signed-off-by: NJunio C Hamano <junio@twinsun.com>

This extends the ref reading to understand a "symbolic ref": a ref file
that starts with "ref: " and points to another ref file, and thus
introduces the notion of ref aliases.

This is in preparation of allowing HEAD to eventually not be a symlink,
but one of these symbolic refs instead.

[jc: Linus originally required the prefix to be "ref: " five bytes
 and nothing else, but I changed it to allow and strip any number of
 leading whitespaces to match what update-ref.c does.]
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Because there is no reason not to, and this makes things a bit
safer when running "git prune".

[jc: I do not necessarily agree with the reasoning of the
original author that it is a good way to keep "git prune" from
stomping on objects to have a symlink that points at .git/refs
of the repository A in the .git/refs of the repository B when
repository A borrows object database from repository B.  For one
thing, the object database that everybody borrows objects from
may not even have its own .git/refs hierarchy.  Come to think of
it, maybe we should disallow symlink inside .git/refs hierarchy;
we update the files there by creat/rename pair, so having
symlinks would not work anyway when you do anything that would
update them.]
Signed-off-by: NJunio C Hamano <junkio@cox.net>

GCC's format __attribute__ is good for checking errors, especially
with -Wformat=2 parameter. This fixes most of the reported problems
against 2005-08-09 snapshot.

It always uses a git-relative pathname, ie "refs/heads/master" instead of
".git/refs/heads/master" or whatever your GIT_DIR might be.

This way when we send refs back-and-forth between repositories, there's
never any question about GIT_DIR on either side.

It did a "for_each_ref()" in addition to the HEAD case, which was a
left-over from an early broken test.

"git_path()" returns a static pathname pointer into the git directory
using a printf-like format specifier.

"head_ref()" works like "for_each_ref()", except for just the HEAD.

Remove the "./" at the head, it just looks much nicer.

It needed to take the GIT_DIR information into account, something that
the original receive-pack usage just never cared about.

This turns it into a generic "do xyz for each ref" library function.

This patch adds code to read a hash out of a specified file under
{GIT_DIR}/refs/, and to write such files atomically and optionally with an
compare and lock.
Signed-off-by: NDaniel Barkalow <barkalow@iabervon.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>