check_sha1_signature: check return value from read_istream

diff --git a/git-difftool.perl b/git-difftool.perl
index edd0493a08b501d60c04044e79a9e0b096d77953..12231fbc6708971f6350006c710124bd369de7ab 100755 (executable)
--- a/git-difftool.perl
+++ b/git-difftool.perl
@@ -59,57 +59,16 @@ sub find_worktree
        return $worktree;
 }
 
-sub filter_tool_scripts
-{
-       my ($tools) = @_;
-       if (-d $_) {
-               if ($_ ne ".") {
-                       # Ignore files in subdirectories
-                       $File::Find::prune = 1;
-               }
-       } else {
-               if ((-f $_) && ($_ ne "defaults")) {
-                       push(@$tools, $_);
-               }
-       }
-}
-
 sub print_tool_help
 {
-       my ($cmd, @found, @notfound, @tools);
-       my $gitpath = Git::exec_path();
-
-       find(sub { filter_tool_scripts(\@tools) }, "$gitpath/mergetools");
-
-       foreach my $tool (@tools) {
-               $cmd  = "TOOL_MODE=diff";
-               $cmd .= ' && . "$(git --exec-path)/git-mergetool--lib"';
-               $cmd .= " && get_merge_tool_path $tool >/dev/null 2>&1";
-               $cmd .= " && can_diff >/dev/null 2>&1";
-               if (system('sh', '-c', $cmd) == 0) {
-                       push(@found, $tool);
-               } else {
-                       push(@notfound, $tool);
-               }
-       }
-
-       print << 'EOF';
-'git difftool --tool=<tool>' may be set to one of the following:
-EOF
-       print "\t$_\n" for (sort(@found));
+       my $cmd = 'TOOL_MODE=diff';
+       $cmd .= ' && . "$(git --exec-path)/git-mergetool--lib"';
+       $cmd .= ' && show_tool_help';
 
-       print << 'EOF';
-
-The following tools are valid, but not currently available:
-EOF
-       print "\t$_\n" for (sort(@notfound));
-
-       print << 'EOF';
-
-NOTE: Some of the tools listed above only work in a windowed
-environment. If run in a terminal-only session, they will fail.
-EOF
-       exit(0);
+       # See the comment at the bottom of file_diff() for the reason behind
+       # using system() followed by exit() instead of exec().
+       my $rc = system('sh', '-c', $cmd);
+       exit($rc | ($rc >> 8));
 }
 
 sub exit_cleanup
@@ -377,7 +336,7 @@ sub main
        }
        if ($opts{gui}) {
                my $guitool = Git::config('diff.guitool');
-               if (length($guitool) > 0) {
+               if (defined($guitool) && length($guitool) > 0) {
                        $ENV{GIT_DIFF_TOOL} = $guitool;
                }
        }