remove usage of `basename` on `--help` argument

[Bhupesh-V]

Is your feature request related to a problem? Please describe.

Currently when printing help text for ugit ugit --help, we figure out the basename of the current running script. Which seems and looks good but adds unnecessary overhead of external command usage.

 $(basename "${BASH_SOURCE[0]}")

More about BASH_SOURCE

BASH_SOURCE
                An array variable whose members are the source filenames where
                the corresponding shell function names in the FUNCNAME array
                variable are defined.  The shell function ${FUNCNAME[$i]} is
*               defined in the file ${BASH_SOURCE[$i]} and called from
*               ${BASH_SOURCE[$i+1]}.

Describe the solution you'd like

Just reference "ugit" string directly.

Describe alternatives you've considered

No response