convert: rewrite calls to Git to use the new shelling mechanism (SEC)
CVE-2016-3069 (2/5)
One test output changed because we were ignoring git return code in numcommits
before.
convert: add new, non-clowny interface for shelling out to git (SEC)
CVE-2016-3069 (1/5)
To avoid shell injection and for the sake of simplicity let's use the
common.commandline for calling git.