C++ libraries in remote repos don't need to set include paths

Fixes #445, based on https://github.com/bazelbuild/bazel/compare/master...ulfjack:cpp-include-path.

RELNOTES: C++ libraries no longer need includes = ["."] (or similar copts) to include paths relative to a remote repository's root.

--
MOS_MIGRATED_REVID=107593486

2 files changed, 8 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
index 0b5fb442cd..cce02514eb 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
@@ -743,8 +743,11 @@ public final class CcLibraryHelper {
     // generated files. It is important that the execRoot (EMPTY_FRAGMENT) comes
     // before the genfilesFragment to preferably pick up source files. Otherwise
     // we might pick up stale generated files.
-    contextBuilder.addQuoteIncludeDir(PathFragment.EMPTY_FRAGMENT);
-    contextBuilder.addQuoteIncludeDir(ruleContext.getConfiguration().getGenfilesFragment());
+    PathFragment repositoryPath =
+        ruleContext.getLabel().getPackageIdentifier().getRepository().getPathFragment();
+    contextBuilder.addQuoteIncludeDir(repositoryPath);
+    contextBuilder.addQuoteIncludeDir(
+        ruleContext.getConfiguration().getGenfilesFragment().getRelative(repositoryPath));
 
     for (PathFragment systemIncludeDir : systemIncludeDirs) {
       contextBuilder.addSystemIncludeDir(systemIncludeDir);
diff --git a/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java b/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
index 434cdcfc2c..97221abf6f 100644
--- a/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
+++ b/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
@@ -379,6 +379,9 @@ public final class PathFragment implements Comparable<PathFragment>, Serializabl
    * with no path normalization or I/O performed.
    */
   public PathFragment getRelative(PathFragment otherFragment) {
+    if (otherFragment == EMPTY_FRAGMENT) {
+      return this;
+    }
     return otherFragment.isAbsolute()
         ? otherFragment
         : new PathFragment(this, otherFragment);