Add "local_generator"

This generator can be used by .spec file, which ships their own
generators:

~~~
Source1: generator.req
%global __local_generator_requires bash %{SOURCE1}
%global __local_generator_path .*
~~~

Resolves #782

build/rpmfc.c

@@ -1184,13 +1184,15 @@ static int initAttrs(rpmfc fc)
 
     /* Discover known attributes from pathnames + initialize them */
     if (rpmGlob(attrPath, NULL, &files) == 0) {
-	nattrs = argvCount(files);
+	int nfiles = argvCount(files);
+	nattrs = nfiles + 1;
 	fc->atypes = xcalloc(nattrs + 1, sizeof(*fc->atypes));
-	for (int i = 0; i < nattrs; i++) {
+	for (int i = 0; i < nfiles; i++) {
 	    char *bn = basename(files[i]);
 	    bn[strlen(bn)-strlen(".attr")] = '\0';
 	    fc->atypes[i] = rpmfcAttrNew(bn);
 	}
+	fc->atypes[nattrs - 1] = rpmfcAttrNew("local_generator");
 	fc->atypes[nattrs] = NULL;
 	argvFree(files);
     }

tests/rpmbuild.at

@@ -860,6 +860,23 @@ runroot rpm -qp --requires /build/RPMS/noarch/shebang-0.1-1.noarch.rpm|grep -v ^
 [])
 RPMTEST_CLEANUP
 
+AT_SETUP([Local dependency generator])
+AT_KEYWORDS([build])
+RPMTEST_CHECK([
+RPMDB_INIT
+
+runroot rpmbuild -bb --quiet \
+		--define '__local_generator_provides() foo(%{basename:%{1}})' \
+		--define '__local_generator_path .*' \
+		/data/SPECS/shebang.spec
+runroot rpm -qp --provides /build/RPMS/noarch/shebang-0.1-1.noarch.rpm|grep -v ^rpmlib
+],
+[0],
+[foo(shebang)
+],
+[])
+RPMTEST_CLEANUP
+
 AT_SETUP([elf dependencies])
 AT_KEYWORDS([build])
 RPMDB_INIT