dirstate: add a test showing a symlink problem

Summary:
Files with one of its directory being a symlink should be considered as
outside the repo. The test demonstrates that with fsmonitor, all dirstate
implementations have problems showing auditfail [1] files.

[1]: https://www.mercurial-scm.org/repo/hg/rev/2cbd27f4f3c4

Reviewed By: DurhamG

Differential Revision: D8721021

fbshipit-source-id: fcb9808b637993c4d0c173d771fd7220afb52d83

tests/test-dirstate-symlink.t

@@ -0,0 +1,49 @@
+#require symlink
+
+#testcases v0 v1 v2
+
+#if v0
+  $ setconfig format.dirstate=0
+#endif
+
+#if v1
+  $ setconfig format.dirstate=1
+#endif
+
+#if v2
+  $ setconfig format.dirstate=2
+#endif
+
+  $ newrepo
+  $ mkdir a b
+  $ touch a/x
+
+  $ hg ci -m init -A a/x
+
+Replace the directory with a symlink
+
+  $ mv a/x b/x
+  $ rmdir a
+  $ ln -s b a
+
+"! a/x" should be shown, as it is implicitly removed
+
+  $ hg status
+  ! a/x
+  ? a
+  ? b/x
+
+  $ hg ci -m rename -A .
+  adding a
+  removing a/x
+  adding b/x
+
+
+#if fsmonitor
+BUG: fsmonitor "hg status" shows a/x
+
+  $ hg status
+  ? a/x
+#else
+  $ hg status
+#endif