Jeff King 370e5ad65e create_symref: use existing ref-lock code ... The create_symref() function predates the existence of "struct lock_file", let alone the more recent "struct ref_lock". Instead, it just does its own manual dot-locking. Besides being more code, this has a few downsides: - if git is interrupted while holding the lock, we don't clean up the lockfile - we don't do the usual directory/filename conflict check. So you can sometimes create a symref "refs/heads/foo/bar", even if "refs/heads/foo" exists (namely, if the refs are packed and we do not hit the d/f conflict in the filesystem). This patch refactors create_symref() to use the "struct ref_lock" interface, which handles both of these things. There are a few bonus cleanups that come along with it: - we leaked ref_path in some error cases - the symref contents were stored in a fixed-size buffer, putting an artificial (albeit large) limitation on the length of the refname. We now write through fprintf, and handle refnames of any size. - we called adjust_shared_perm only after the file was renamed into place, creating a potential race with readers in a shared repository. The lockfile code now handles this when creating the lockfile, making it atomic. - the legacy prefer_symlink_refs path did not do any locking at all. Admittedly, it is not atomic from a reader's perspective (as it unlinks and re-creates the symlink to overwrite), but at least it cannot conflict with other writers now. - the result of this patch is hopefully more readable. It eliminates three goto labels. Two were for error checking that is now simplified, and the third was to reach shared code that has been pulled into its own function. Signed-off-by: Jeff King <peff@peff.net> Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>		2015-12-29 10:33:31 -08:00
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files-backend.c	create_symref: use existing ref-lock code	2015-12-29 10:33:31 -08:00
refs-internal.h	refs: break out ref conflict checks	2015-11-20 04:52:01 -05:00