Create Bazel symlink forest in a separate process.
This helps with incrementality a lot: the symlink forest must depend on
almost every directory in the source tree so that if a new file is added
or removed from *anywhere*, it is regenerated.
Previously, we couldn't do this without invoking bp2build, which is
quite wasteful because bp2build takes way more time than the symlink
forest creation, even though we do the latter in a very suboptimal way
at the moment.
This means that if a source file is added or removed (which does not
affect globs), we don't pay the cost of bp2build anymore.
Also refactored symlink_forest.go on the side. Too much state was being
passed around in arguments.
This change reimplements aosp/2263423 ; the semantics of not touching an
output file is the exact same as order-only inputs and the latter is a
bit fewer lines of code.
Test: Presubmits.
Change-Id: I565c580df8a01bacf175d56747c3f50743d4a4d4
diff --git a/android/config.go b/android/config.go
index 1ed405b..df2c767 100644
--- a/android/config.go
+++ b/android/config.go
@@ -75,6 +75,9 @@
// Don't use bazel at all during module analysis.
AnalysisNoBazel SoongBuildMode = iota
+ // Symlink fores mode: merge two directory trees into a symlink forest
+ SymlinkForest
+
// Bp2build mode: Generate BUILD files from blueprint files and exit.
Bp2build