Improve includes in the amalgamation script

Now it also tries to find the included file relatively to the "parent"
file. This is required for amalgamation of the frozen into mjs, since
`frozen.c` includes `frozen.h` instead of `frozen/frozen.h`.

PUBLISHED_FROM=8f670a1509a30cfdfb22e454b7851f4cf28fb98d

tools/amalgam.py

@@ -61,10 +61,11 @@ parser.add_argument('-I', default=".", dest='include_path', help='include path')
 parser.add_argument('sources', nargs='*', help='sources')
 
 class File(object):
-    def __init__(self, name):
+    def __init__(self, name, parent_name):
         self.name = name
+        self.parent_name = parent_name
         self.buf = StringIO()
-        emit_file(self.buf, self.name)
+        emit_file(self.buf, self.name, self.parent_name)
 
     def emit(self):
         print self.buf.getvalue(),
@@ -79,14 +80,22 @@ already_included = set()
 
 ignore_files = [i.strip() for i in args.ignore.split(',')]
 
-def should_ignore(name):
+def should_ignore(name, parent_name):
     return (name in already_included
-            or not (args.strict or os.path.exists(resolve(name)))
+            or not (args.strict or os.path.exists(resolve(name, parent_name)))
             or name in ignore_files)
 
-def resolve(path):
+def resolve(path, parent_name):
+    path_from_parent = None
+    if parent_name != None and not os.path.isabs(path):
+        # calculate the path relative to the "parent_name" file, i.e. to the file
+        # which includes the current one.
+        path_from_parent = os.path.join(os.path.dirname(parent_name), path)
+
     if os.path.isabs(path) or os.path.exists(path):
         p = path
+    elif path_from_parent != None and os.path.exists(path_from_parent):
+        p = path_from_parent
     else:
         p = os.path.join(args.include_path, path)
     if os.path.exists(p) and not args.norel:
@@ -94,40 +103,40 @@ def resolve(path):
     # print >>sys.stderr, '%s -> %s (cwd %s)' % (path, p, os.getcwd())
     return p
 
-def emit_line_directive(out, name):
+def emit_line_directive(out, name, parent_name):
     print >>out, '''#ifdef %(prefix)s_MODULE_LINES
 #line 1 "%(name)s"
 #endif''' % dict(
     prefix = args.prefix,
-    name = resolve(name),
+    name = resolve(name, parent_name),
 )
 
-def emit_body(out, name):
-    path = resolve(name)
-    if not args.strict and not os.path.exists(path):
+def emit_body(out, name, parent_name):
+    resolved_name = resolve(name, parent_name)
+    if not args.strict and not os.path.exists(resolved_name):
         print >>out, '#include "%s"' % (name,)
         return
 
-    with open(resolve(name)) as f:
+    with open(resolved_name) as f:
         for l in f:
             match = re.match('( *#include "(.*)")', l)
             if match:
-                all, path = match.groups()
+                all, path_to_include = match.groups()
                 if args.autoinc:
-                    if not should_ignore(path):
-                        already_included.add(path)
-                        includes.append(File(path))
+                    if not should_ignore(path_to_include, parent_name):
+                        already_included.add(path_to_include)
+                        includes.append(File(path_to_include, resolved_name))
                 print >>out, '/* Amalgamated: %s */' % (all,)
             else:
                 print >>out, l,
 
 
-def emit_file(out, name):
-    emit_line_directive(out, name)
-    emit_body(out, name)
+def emit_file(out, name, parent_name):
+    emit_line_directive(out, name, parent_name)
+    emit_body(out, name, parent_name)
 
 for i in args.sources:
-    sources.append(File(i))
+    sources.append(File(i, None))
 
 if args.first:
     for inc in reversed(args.first.split(',')):