The make-release script should balk if it sees that you have given it a tag that is different than $wgVersion. Alternatively, maybe it could grab the tag from $wgVersion if it is just given a branch to build.
Related Gerrit Patches:
|mediawiki/tools/release : master||Move to `git archive` like model for MediaWiki releases|
|Declined||None||T76896 Wiki Release Team First Quarter 2015 Quarterly Review|
|Resolved||Qgil||T76672 Wiki Release Team December Goals|
|Resolved||Qgil||T782 Wiki Release Team November 2014 Goals|
|Open||None||T974 Automate Testing of MediaWiki Tarball releases|
|Resolved||Legoktm||T949 update make-release to refuse to work if tag != $wgVersion|