Make @load statements recognize relative paths.

For example a script can do "@load ./foo" to load a script named
foo.bro that lives in the same directory or "@load ../bar" to load
a script named bar.bro in the parent directory, even if those
directories are not contained in BROPATH.

src/scan.l

@@ -9,6 +9,7 @@
 #include <string>
 #include <algorithm>
 #include <sys/stat.h>
+#include <libgen.h>
 
 #include "input.h"
 #include "util.h"
@@ -39,6 +40,7 @@ int line_number = 1;
 const char* filename = 0;
 BroDoc* current_reST_doc = 0;
 static BroDoc* last_reST_doc = 0;
+string current_scanned_file_path;
 
 char last_tok[128];
 
@@ -102,6 +104,7 @@ public:
 	int line;
 	int level;
 	BroDoc* doc;
+	string path;
 };
 
 // A stack of input buffers we're scanning.  file_stack[len-1] is the
@@ -613,6 +616,10 @@ static int load_files_with_prefix(const char* orig_file)
 			else
 				file_stack.append(new FileInfo);
 
+			char* tmp = copy_string(full_filename);
+			current_scanned_file_path = dirname(tmp);
+			delete [] tmp;
+
 			if ( generate_documentation )
 				{
 				current_reST_doc = new BroDoc(bropath_subpath, full_filename);
@@ -895,6 +902,7 @@ FileInfo::FileInfo(string arg_restore_module)
 	name = ::filename;
 	line = ::line_number;
 	doc = ::current_reST_doc;
+	path = current_scanned_file_path;
 	}
 
 FileInfo::~FileInfo()
@@ -907,6 +915,7 @@ FileInfo::~FileInfo()
 	yylloc.first_line = yylloc.last_line = line_number = line;
 	last_reST_doc = current_reST_doc;
 	current_reST_doc = doc;
+	current_scanned_file_path = path;
 
 	if ( restore_module != "" )
 		current_module = restore_module;

src/util.cc

@@ -868,11 +868,20 @@ void get_policy_subpath(const char* dir, const char* file, const char** subpath)
 	delete [] tmp;
 	}
 
+extern string current_scanned_file_path;
+
 FILE* search_for_file(const char* filename, const char* ext,
 			const char** full_filename, bool load_pkgs,
 			const char** bropath_subpath)
 	{
-	if ( filename[0] == '/' || filename[0] == '.' )
+	// If the file is a literal absolute path we don't have to search,
+	// just return the result of trying to open it.  If the file is
+	// might be a relative path, check first if it's a real file that
+	// can be referenced from cwd, else we'll try to search for it based
+	// on what path the currently-loading script is in as well as the
+	// standard BROPATH paths.
+	if ( filename[0] == '/' ||
+	    (filename[0] == '.' && access(filename, R_OK) == 0) )
 		{
 		if ( bropath_subpath )
 			{
@@ -886,6 +895,12 @@ FILE* search_for_file(const char* filename, const char* ext,
 	char path[1024], full_filename_buf[1024];
 	safe_strncpy(path, bro_path(), sizeof(path));
 
+	// append the currently loading script's path to BROPATH so that
+	// @loads can be referenced relatively
+	if ( current_scanned_file_path != "" )
+		safe_snprintf(path, sizeof(path), "%s:%s", path,
+		              current_scanned_file_path.c_str());
+
 	char* dir_beginning = path;
 	char* dir_ending = path;
 	int more = *dir_beginning != '\0';

testing/btest/Baseline/core.load-relative/output

@@ -0,0 +1,3 @@
+bar loaded
+baz loaded
+foo loaded

testing/btest/core/load-relative.bro

@@ -0,0 +1,10 @@
+# A test of relative-path-based @load'ing
+
+# @TEST-EXEC: mkdir foo
+# @TEST-EXEC: echo "@load ./bar" > foo/foo.bro
+# @TEST-EXEC: echo "@load ../baz" >> foo/foo.bro
+# @TEST-EXEC: echo 'print "foo loaded";' >> foo/foo.bro
+# @TEST-EXEC: echo 'print "bar loaded";' > foo/bar.bro
+# @TEST-EXEC: echo 'print "baz loaded";' > baz.bro
+# @TEST-EXEC: bro foo/foo >output
+# @TEST-EXEC: btest-diff output