Add support for default extension specification, trailing dot escaping

For example:

cxx{*}: extension = cxx

cxx{foo}         # foo.cxx
cxx{foo.test}    # foo.test      (probably what we want...)
cxx{foo.test...} # foo.test.cxx  (... is this)
cxx{foo..}       # foo.
cxx{foo....}     # foo..
cxx{foo.....}    # error (must come in escape pair)

1 files changed, 5 insertions, 6 deletions

diff --git a/build2/test/target.cxx b/build2/test/target.cxx
index a517240..57e2cb5 100644
--- a/build2/test/target.cxx
+++ b/build2/test/target.cxx
@@ -24,18 +24,17 @@ namespace build2
     testscript_target_pattern (const target_type&,
                                const scope&,
                                string& v,
+                               optional<string>& e,
                                bool r)
     {
-      size_t p (path::traits::find_extension (v));
-
       if (r)
       {
-        assert (p != string::npos);
-        v.resize (p);
+        assert (e);
+        e = nullopt;
       }
-      else if (p == string::npos && v != "testscript")
+      else if (!e && v != "testscript")
       {
-        v += ".test";
+        e = "test";
         return true;
       }