gitweb: make remote_heads config setting work

Git configuration items can not contain underscores in their section
and bottom-level variable name; the 'remote_heads' feature can not
be enabled on a per-repository basis with that name.

This changes the git-config option to be `gitweb.remoteheads` but does
not change the gitweb.conf option, to avoid backwards compatibility
issues.  We strip underscores from keys before looking through
git-config output for them.

An existing check on keynames was overly eager to reject non-word
letters, but if we ever start using three-level names, the middle
level string can contain almost anything, so fix that as well while
we are in the vicinity.

Signed-off-by: Phil Pennock <phil@apcera.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -541,7 +541,7 @@ sub evaluate_uri {
 	# $feature{'remote_heads'}{'default'} = [1];
 	# To have project specific config enable override in $GITWEB_CONFIG
 	# $feature{'remote_heads'}{'override'} = 1;
-	# and in project config gitweb.remote_heads = 0|1;
+	# and in project config gitweb.remoteheads = 0|1;
 	'remote_heads' => {
 		'sub' => sub { feature_bool('remote_heads', @_) },
 		'override' => 0,
@@ -2697,12 +2697,15 @@ sub git_get_project_config {
 	# only subsection, if exists, is case sensitive,
 	# and not lowercased by 'git config -z -l'
 	if (my ($hi, $mi, $lo) = ($key =~ /^([^.]*)\.(.*)\.([^.]*)$/)) {
+		$lo =~ s/_//g;
 		$key = join(".", lc($hi), $mi, lc($lo));
+		return if ($lo =~ /\W/ || $hi =~ /\W/);
 	} else {
 		$key = lc($key);
+		$key =~ s/_//g;
+		return if ($key =~ /\W/);
 	}
 	$key =~ s/^gitweb\.//;
-	return if ($key =~ m/\W/);
 
 	# type sanity check
 	if (defined $type) {