I don't understand your point, how does this happen twi ... ohhh because dependent files get changed as well? Surely this is just a matter of how you specify your dependencies?
imagine your project structure is the following :
header.h
src1.cpp
src2.cpp
src3.cpp
1. change header.h
2. rebuild. this rebuilds all your .cpp because they all use the header - this is fine and expected.
3. git pull --rebase because your coworker fixed a bug in src1.cpp which landed in the master branch
4. here when you rebuild with make, even though only src1.cpp has changed from your point of view, everything actually gets rebuilt because git stashes your change, applies the remote commits and unstashes your change, so header.h's timestamp gets changed again.
yes, me too, but in this case the rebuild happens twice while the header changes only once (from the point of view of the programmer of course, from the point of view of the filesystem it changes twice). If hashes were used this would not be a problem at all.