depends on git-minimal

the-vault does not need all currently existing git buddies like perl, so it
depends on git-minimal to not pull this dependencies with it. For logical
correctness git package should provide git-minimal but I afraid it will be a
random choice what will be selected: feature git-minimal provided by git or
package git-minimal :/

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>