# HG changeset patch
# User Arseniy Alekseyev <aalekseyev@janestreet.com>
# Date 2021-10-14 18:02:08
# Node ID f8dc78716ad2b8357fe5e41a3dbd1acef9d1fa38
# Parent  5c567aca080d255a9d5c4daf44370e59892b61d0

rhg: fix `hg cat` interaction with null revision

Differential Revision: https://phab.mercurial-scm.org/D11664

diff --git a/rust/hg-core/src/revlog/revlog.rs b/rust/hg-core/src/revlog/revlog.rs
--- a/rust/hg-core/src/revlog/revlog.rs
+++ b/rust/hg-core/src/revlog/revlog.rs
@@ -133,6 +133,9 @@ impl Revlog {
     /// Returns the node ID for the given revision number, if it exists in this
     /// revlog
     pub fn node_from_rev(&self, rev: Revision) -> Option<&Node> {
+        if rev == NULL_REVISION {
+            return Some(&NULL_NODE);
+        }
         Some(self.index.get_entry(rev)?.hash())
     }
 
diff --git a/tests/test-rhg.t b/tests/test-rhg.t
--- a/tests/test-rhg.t
+++ b/tests/test-rhg.t
@@ -129,8 +129,8 @@ Specifying revisions by changeset ID
   $ $NO_FALLBACK rhg cat -r d file-2
   2
   $ $NO_FALLBACK rhg cat -r 0000 file-2
-  abort: invalid revision identifier: 0000
-  [255]
+  file-2: no such file in rev 000000000000
+  [1]
 
 Cat files
   $ cd $TESTTMP