Merge remote-tracking branch 'aosp/upstream'

* aosp/upstream:
  Add --empty_ninja_file for test usecases
  Update README.md

Test: prebuilts/build-tools/build-prebuilts.sh
Change-Id: I36f082a27b3d7067517af9d55085bfb383df9c68

4 files changed, 15 insertions, 9 deletions

diff --git a/README.md b/README.md
index 3678f2c..029a57d 100644
--- a/README.md
+++ b/README.md
@@ -12,13 +12,12 @@ your Makefile to a ninja file.
 How to use for Android
 ----------------------
 
-Now AOSP has kati and ninja, so all you have to do is
-
-    % export USE_NINJA=true
+For Android-N+, ckati and ninja is used automatically. There is a prebuilt
+checked in under prebuilts/build-tools that is used.
 
 All Android's build commands (m, mmm, mmma, etc.) should just work.
 
-How to use for Android (deprecated way)
+How to use for Android (deprecated -- only for Android M or earlier)
 ----------------------
 
 Set up kati:
@@ -33,7 +32,7 @@ Build Android:
     % cd <android-directory>
     % source build/envsetup.sh
     % lunch <your-choice>
-    % ~/src/kati/m2n --kati_stats  # Use --goma if you are a Googler.
+    % ~/src/kati/m2n --kati_stats
     % ./ninja.sh
 
 You need ninja in your $PATH.
diff --git a/flags.cc b/flags.cc
index 07b5748..54828e5 100644
--- a/flags.cc
+++ b/flags.cc
@@ -82,6 +82,8 @@ void Flags::Parse(int argc, char** argv) {
       enable_kati_warnings = true;
     } else if (!strcmp(arg, "--ninja")) {
       generate_ninja = true;
+    } else if (!strcmp(arg, "--empty_ninja_file")) {
+      generate_empty_ninja = true;
     } else if (!strcmp(arg, "--gen_all_targets")) {
       gen_all_targets = true;
     } else if (!strcmp(arg, "--regen")) {
diff --git a/flags.h b/flags.h
index 025979a..62865a3 100644
--- a/flags.h
+++ b/flags.h
@@ -32,6 +32,7 @@ struct Flags {
   bool enable_stat_logs;
   bool gen_all_targets;
   bool generate_ninja;
+  bool generate_empty_ninja;
   bool is_dry_run;
   bool is_silent_mode;
   bool is_syntax_check_only;
diff --git a/ninja.cc b/ninja.cc
index 0b87d5c..90e56c8 100644
--- a/ninja.cc
+++ b/ninja.cc
@@ -629,8 +629,10 @@ class NinjaGenerator {
     }
     tp->Wait();
 
-    for (const ostringstream& buf : bufs) {
-      fprintf(fp_, "%s", buf.str().c_str());
+    if (!g_flags.generate_empty_ninja) {
+      for (const ostringstream& buf : bufs) {
+        fprintf(fp_, "%s", buf.str().c_str());
+      }
     }
 
     SymbolSet used_env_vars(Vars::used_env_vars());
@@ -652,8 +654,10 @@ class NinjaGenerator {
         default_targets += EscapeBuildTarget(s);
       }
     }
-    fprintf(fp_, "\n");
-    fprintf(fp_, "default %s\n", default_targets.c_str());
+    if (!g_flags.generate_empty_ninja) {
+      fprintf(fp_, "\n");
+      fprintf(fp_, "default %s\n", default_targets.c_str());
+    }
 
     fclose(fp_);
   }