GIT v(+) database versioning question

Hello,

may I ask a question: what would be the best way to achieve this with GIT:

Database versioning scripts shall be (1) numbered (due to DBmaintain)  
and (2) incremental.

ad 1) When a developer commits a script, I should get the next higher 
number
than the last committed script. E.g. 045_customers.SQL, 046_orders.SQL etc

ad 2) Scripts, which are once committed, should be immutable -- developers
should not be able to change them. They can only add new scripts.

Many thanks in advance,
V. Prochazka