If one contributor make a modification in GIT he'll add a modification with the latest 12.179 commits?
>> yes
Other way... supposing that an new contributor make a change on pc.c that a old contributor does in the commit 12.179 the current contributor will modify with the lastest or they uses different branches?
>> I would say, when the current contributor pushes the changes, GIT will tell him that the file was already modified.
e.g:
pc.c's version is 1.0.0. then, Contributor A made changes.
during the same time, Contributor B has changed pc.c AND pushed it.
server will keep note on the version, changing it to 1.0.1 (or whatever)
then, when Contributor A do GIT PUSH, GIT will check the original file, if it is the same or not. since Contrib A's pc.c version is 1.0.0 and the one on server is already 1.0.1, Contributor A's push will be declined and he will be notified.