branch: split off function that writes tracking info and commit subject
Introduce a add_verbose_info function that takes care of adding
- an abbreviated object name;
- a summary of the form [ahead x, behind y] of the relationship
to the corresponding upstream branch;
- a one line commit subject
for the tip commit of a branch, for use in "git branch -v" output.
No functional change intended. This just unindents the code a little
and makes it easier to skip on first reading.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>