Log ref updates to logs/refs/<ref>
If config parameter core.logAllRefUpdates is true or the log
file already exists then append a line to ".git/logs/refs/<ref>"
whenever git-update-ref <ref> is executed. Each log line contains
the following information:
oldsha1 <SP> newsha1 <SP> committer <LF>
where committer is the current user, date, time and timezone in
the standard GIT ident format. If the caller is unable to append
to the log file then git-update-ref will fail without updating <ref>.
An optional message may be included in the log line with the -m flag.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>