Implement automatic subproject discovery

Currently we only capture their directories without the project
names. We will need project names when we hook import search into
this.

1 files changed, 7 insertions, 0 deletions

diff --git a/build/b.cxx b/build/b.cxx
index 1650a73..593fbc1 100644
--- a/build/b.cxx
+++ b/build/b.cxx
@@ -296,6 +296,13 @@ main (int argc, char* argv[])
 
           if (!src_base.empty ())
           {
+            // Make sure it exists. While we will fail further down
+            // if it doesn't, the diagnostics could be confusing (e.g.,
+            // unknown operation because we don't load bootstrap.build).
+            //
+            if (!dir_exists (src_base))
+              fail << "src_base directory " << src_base << " does not exist";
+
             if (src_base.relative ())
               src_base = work / src_base;