Bug tracking.

[J]

Have to use labels for bug tacking right?

Whe isn't there a unique commit number for each and every commit ever done?

So for example I change main.c, and commit, this records change number 2 on
the file

Someone else changes main.c and list.c and fish.c this records number 3 on
main.c list.c and fish.c

This is a sort of automatic labelling, thereby you can use the numbers in
your bug tracking software to refer to the changes without having to label
everything.