graph: Assume all root nodes if no target given.

This way we can generate the complete graph.

2 files changed, 22 insertions, 7 deletions

diff --git a/manual.asciidoc b/manual.asciidoc
index 7ea3da8..cf7b2c8 100644
--- a/manual.asciidoc
+++ b/manual.asciidoc
@@ -311,7 +311,8 @@ feature requires a Python installation.
 `graph`:: output a file in the syntax used by `graphviz`, a automatic
 graph layout tool.  Use it like: +ninja -t graph _target_ | dot -Tpng
 -ograph.png /dev/stdin+ .  In the Ninja source tree, `ninja graph`
-generates an image for Ninja itself.
+generates an image for Ninja itself.  If no target is given generate a
+graph for all root targets.
 
 `targets`:: output a list of targets either by rule or by depth.  If used
 like this +ninja -t targets rule _name_+ it prints the list of targets
diff --git a/src/ninja.cc b/src/ninja.cc
index 5a0c00d..c4f78ab 100644
--- a/src/ninja.cc
+++ b/src/ninja.cc
@@ -106,14 +106,28 @@ int CmdGraph(State* state, int argc, char* argv[]) {
   int status = 0;
   GraphViz graph;
   graph.Start();
-  for (int i = 0; i < argc; ++i) {
-    Node* node = state->LookupNode(argv[i]);
-    if (node)
-      graph.AddTarget(node);
-    else {
-      Error("unknown target '%s'", argv[i]);
+  if (argc == 0) {
+    string err;
+    vector<Node*> root_nodes = state->RootNodes(&err);
+    if (err.empty()) {
+      for (vector<Node*>::const_iterator n = root_nodes.begin();
+           n != root_nodes.end();
+           ++n)
+        graph.AddTarget(*n);
+    } else {
+      Error("%s", err.c_str());
       status = 1;
     }
+  } else {
+    for (int i = 0; i < argc; ++i) {
+      Node* node = state->LookupNode(argv[i]);
+      if (node)
+        graph.AddTarget(node);
+      else {
+        Error("unknown target '%s'", argv[i]);
+        status = 1;
+      }
+    }
   }
   graph.Finish();
   return status;