Okay, take it back: imagine four programmers: A,B,C and D. A asks B to insert one more variable into include file because A program needs to send B more data.........

How on earth will anything work if there is not a common definition of what is common.

My way
The updates of the .h/.inc file are so rare that the overhead of stating that only programmer E is allowed to modify is extremely nominal. However, if you code by "throwing code in" without any preset plan I can see the problem.

what must be Olegs way based on his post
Oleg, in your example you would need the following .h/.inc files
A alone
A shared with B
A shared with B and C
A shared with B and D
A shared with B and C and D
A shared with C
A shared with D
A shared with C and D
B alone
B shared with C
B shared with D
B shared with C and D
C alone
C shared with D
D alone

If that is the easy way then I must be wasting an awful lot of time.

Erik