send-email: drop misleading function prototype

send-email: drop misleading function prototype

The subroutine check_file_rev_conflict() is called from two places,
both of which expects to pass a single scalar variable and see if
that can be interpreted as a pathname or a revision name.  It is
defined with a function prototype ($) to force a scalar context
while evaluating the arguments at the calling site but it does not
help the current calling sites.  The only effect it has is to hurt
future calling sites that may want to build an argument list in an
array variable and call it as check_file_rev_confict(@args).

Drop the misleading prototype, as Perlcritic suggests.

While at it, rename the function to avoid new call sites unaware of
this change arising and add a comment clarifying what this function
is for.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>