tg-tag: handle reflog entries with extra tabs

tg-tag: handle reflog entries with extra tabs

It's very possible for a reflog entry to have more than one
tab in it.

The actual format of the reflog is one entry per line as detailed
in the `git help update-ref` documentation.

That documentation overlooks the possibility of there being more
than one "TAB" present in a single line (i.e. entry) of a reflog.

The relevant code that actually parses these lines can be found in
the Git file refs/files-backend.c in the show_one_reflog_ent function.

Behave more like the show_one_reflog_ent function when parsing
reflog entry lines to avoid any confusion over where the optional
message actually starts (if it's present).

Toggle the two affected unit tests in t6102 from `test_expect_failure`
to `test_expect_success` as they now pass with this change.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>