Disable tabline if there's no tab or for particular filetype

[mabugaj]

It would nice to have an option to disable tabline if there's no tab to show or for particular filetype (startify or alpha).

Good description is native nvim showtabline option:

'showtabline' 'stal' number (default 1)
global
The value of this option specifies when the line with tab page labels
will be displayed:
0: never
1: only if there are at least two tab pages
2: always
This is both for the GUI and non-GUI implementation of the tab pages
line.
See |tab-page| for more information about tab pages.