commit-graph: define GIT_TEST_COMMIT_GRAPH

diff --git a/RelNotes b/RelNotes
index 17d37af54951e3179282cad837ee0beb271eb4e9..5d139ba7f1e20412d24b1397b33e2d4cde016d19 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.7.2.5.txt
\ No newline at end of file
+Documentation/RelNotes/2.19.0.txt
\ No newline at end of file