c++ - Alternatives to git submodule for projects using multiple repositories -

i have 3 repositories: a, b, c (c++ code)

a , b independent projects , both depends on c. association has been made git submodule

i create new project d depends on a , b, c referred 2 times

the project structure similar following:

d |--a |  | |  c | |--b    |    c

since different versions of d correspond different versions of a , b i'd have way keep them synced while checking out between versions.

i thinking removing submodule associations , switch repo a, b , d. make sense? there better way using git?

thank you

if project d contribute repo a , b, can add them submodules project d.

but there no way checkout submodules versions @ same time when checkout version project d. work around use related version of d a , b tags, , execute script checkout a , b related versions.

such v3.0 d version related v1.0 of a , v2.0 of b, can add tags version v3.0.1.0 in a , v3.0.2.0 in b. when checkout v3.0 d, can run script checkout a , b version start v3.0*.
if project d not contribute repo a , b, can remove submodule associations. code a , b subfolders project d , versions of folder a , folder b can sync version project d time.

TY