Remove default value checking in GN, adds getenv function, reorders parameters to rebase_path.

tools/gn/command_args.cc

Index: tools/gn/command_args.cc
diff --git a/tools/gn/command_args.cc b/tools/gn/command_args.cc
index ad1a59699d00aa6fddb14f786f90ab4da5ae3d1a..b5b6eb7c60327a9a7a8ef10b6718c61d17afd42f 100644
--- a/tools/gn/command_args.cc
+++ b/tools/gn/command_args.cc
@@ -42,12 +42,18 @@ size_t BackUpToLineBegin(const std::string& data, size_t offset) {
   return 0;
 }
 
-// Assumes DoesLineBeginWithComment().
-std::string StripCommentFromLine(const base::StringPiece& line) {
-  std::string ret = line.as_string();
-  for (size_t i = 0; i < ret.size(); i++) {
-    if (ret[i] == '#') {
-      ret[i] = ' ';
+// Assumes DoesLineBeginWithComment(), this strips the # character from the
+// beginning and normalizes preceeding whitespace.
+std::string StripHashFromLine(const base::StringPiece& line) {
+  std::string ret;

[viettrungluu, 2014/02/12 23:09:35]

Can't this just be something like:

return "   " + line.substr(line.find('#') + 1).as_string();

+  for (size_t i = 0; i < line.size(); i++) {
+    if (line[i] == '#') {
+      // Replace the # sign and everything before it with 3 spaces, so that
+      // a normal comment that has a space after the # will be indented 4
+      // spaces (which makes our formatting come out nicely). If the comment is
+      // indented from there, we want to preserve that indenting.
+      ret.assign("   ");
+      ret.append(line.substr(i + 1).as_string());
       break;
     }
   }
@@ -79,7 +85,7 @@ void GetContextForValue(const Value& value,
     if (!DoesLineBeginWithComment(line))
       break;
 
-    comment->insert(0, StripCommentFromLine(line) + "\n");
+    comment->insert(0, StripHashFromLine(line) + "\n");
     line_off = previous_line_offset;
   }
 }
@@ -150,6 +156,12 @@ int RunArgs(const std::vector<std::string>& args) {
        i != build_args.end(); ++i)
     sorted_args.insert(*i);
 
+  OutputString(
+      "Available build arguments. Note that the which arguments are declared\n"
+      "and their default values may depend on other arguments or the current\n"
+      "platform and architecture. So setting some values may add, remove, or\n"
+      "change the default value of other values.\n\n");
+
   for (std::map<base::StringPiece, Value>::iterator i = sorted_args.begin();
        i != sorted_args.end(); ++i) {
     PrintArgHelp(i->first, i->second);