In the old version of get-version.js, it replaces the leading 'v',
i.e. |output.stdout.toString().trim().replace(/^v/g, '')|. However,
in the new version of get-git-version.py, it directly replaces all
'v'. Obviously, it does not conform to the original semantics.
Although it will not affect the existing electron version calculation,
it may affect other developers' customized git-tag-version, such as
v0.0.0-dev.xxx, which will lose the 'v' of dev.
