refs: allow "HEAD" as decoration filter
The normalize_glob_ref() method was introduced in 65516f586b693 (log: add option to choose which refs to decorate, 2017-11-21) to help with decoration filters such as --decorate-refs=<filter> and --decorate-refs-exclude=<filter>. The method has not been used anywhere else. At the moment, it is impossible to specify HEAD as a decoration filter since normalize_glob_ref() prepends "refs/" to the filter if it isn't already there. Allow adding HEAD as a decoration filter by allowing the exact string "HEAD" to not be prepended with "refs/". Add a test in t4202-log.sh that would previously fail since the HEAD decoration would exist in the output. It is sufficient to only cover "HEAD" here and not include other special refs like REBASE_HEAD. This is because HEAD is the only ref outside of refs/* that is added to the list of decorations. However, we may want to special-case these other refs in normalize_glob_ref() in the future. Leave a NEEDSWORK comment for now. Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>