Change execution root for external repositories to be ../repo

Some of the important aspect of this change:

* Remote repos in the execution root are under output_base/execroot/repo_name, so the prefix is ../repo_name (to escape the local workspace name).
* Package roots for external repos were previously "output_base/", they are now output_base/external/repo_name (which means source artifacts always have a relative path from their repository).
* Outputs are under bazel-bin/external/repo_name/ (or similarly under genfiles). Note that this is a bit of a change from how this was implemented in the previous cl.

Fixes #1262.

RELNOTES[INC]: Previously, an external repository would be symlinked into the
execution root at execroot/local_repo/external/remote_repo. This changes it to
be at execroot/remote_repo. This may break genrules/Skylark actions that
hardcode execution root paths. If this causes breakages for you, ensure that
genrules are using $(location :target) to access files and Skylark rules are
using http://bazel.io/docs/skylark/lib/File.html's path, dirname, etc.
functions.

Roll forward of bdfd58a.

--
MOS_MIGRATED_REVID=133606309

3 files changed, 5 insertions, 22 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
index b5a699023e..fb4c47f0c8 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
@@ -72,7 +72,7 @@ public final class Label implements Comparable<Label>, Serializable, SkylarkPrin
   public static final PackageIdentifier EXTERNAL_PACKAGE_IDENTIFIER =
       PackageIdentifier.createInMainRepo(EXTERNAL_PACKAGE_NAME);
 
-  public static final String EXTERNAL_PATH_PREFIX = "external";
+  public static final String EXTERNAL_PATH_PREFIX = "..";
 
   private static final Interner<Label> LABEL_INTERNER = Interners.newWeakInterner();
 
@@ -334,7 +334,7 @@ public final class Label implements Comparable<Label>, Serializable, SkylarkPrin
       doc = "Returns the execution root for the workspace of this label, relative to the execroot. "
       + "For instance:<br>"
       + "<pre class=language-python>Label(\"@repo//pkg/foo:abc\").workspace_root =="
-      + " \"external/repo\"</pre>")
+      + " \"../repo\"</pre>")
   public String getWorkspaceRoot() {
     return packageIdentifier.getRepository().getSourceRoot().toString();
   }
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java b/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
index 905866f077..727433a244 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
@@ -124,15 +124,7 @@ public final class PackageIdentifier implements Comparable<PackageIdentifier>, S
   }
 
   public PathFragment getPathUnderExecRoot() {
-    return getSourceRoot();
-  }
-
-  /**
-   * Returns the runfiles/execRoot path for this repository (relative to the x.runfiles/main-repo/
-   * directory).
-   */
-  public PathFragment getRunfilesPath() {
-    return repository.getRunfilesPath().getRelative(pkgName);
+    return repository.getPathUnderExecRoot().getRelative(pkgName);
   }
 
   public PackageIdentifier makeAbsolute() {
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
index ba0f6b407b..cfad122e69 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
@@ -214,8 +214,8 @@ public final class RepositoryName implements Serializable {
   }
 
   /**
-   * Returns the runfiles/execRoot path for this repository. If we don't know the name of this repo
-   * (i.e., it is in the main repository), return an empty path fragment.
+   * Returns the runfiles/execRoot path for this repository: ../reponame. If we don't know the name
+   * of this repo (i.e., it is in the main repository), return an empty path fragment.
    */
   public PathFragment getPathUnderExecRoot() {
     return isDefault() || isMain()
@@ -224,15 +224,6 @@ public final class RepositoryName implements Serializable {
   }
 
   /**
-   * Returns the runfiles path relative to the x.runfiles/main-repo directory.
-   */
-  // TODO(kchodorow): remove once execroot is reorg-ed.
-  public PathFragment getRunfilesPath() {
-    return isDefault() || isMain()
-        ? PathFragment.EMPTY_FRAGMENT : new PathFragment("..").getRelative(strippedName());
-  }
-
-  /**
    * Returns the repository name, with leading "{@literal @}" (or "" for the default repository).
    */
   @Override