difftool: use perl built-ins when testing for msys

I don't even know what $COMSPEC means so let's be safe and use the
same perly $^O test add--interactive uses.  While we're at it, make
git-difftool match the prevalent git-perl style.

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/difftool/git-difftool b/contrib/difftool/git-difftool
index 0deda3a0e41511bb1b71d30d335b4909e8719169..207dd50f2ca4ca328b7233f80b7c350277bc547b 100755 (executable)
--- a/contrib/difftool/git-difftool
+++ b/contrib/difftool/git-difftool
@@ -33,7 +33,10 @@ sub setup_environment
 sub exe
 {
        my $exe = shift;
-       return defined $ENV{COMSPEC} ? "$exe.exe" : $exe;
+       if ($^O eq 'MSWin32' || $^O eq 'msys') {
+               return "$exe.exe";
+       }
+       return $exe;
 }
 
 sub generate_command
@@ -47,7 +50,7 @@ sub generate_command
                        $skip_next = 0;
                        next;
                }
-               if ($arg eq '-t' or $arg eq '--tool') {
+               if ($arg eq '-t' || $arg eq '--tool') {
                        usage() if $#ARGV <= $idx;
                        $ENV{GIT_DIFF_TOOL} = $ARGV[$idx + 1];
                        $skip_next = 1;