Update publish field doc to explain new `cargo publish` behavior

diff --git a/src/doc/src/reference/manifest.md b/src/doc/src/reference/manifest.md
index bac6093f46ad3ecdd8977a2955ac765168e0b228..853ffc3c273a0866676c548d6fa9dbf121637361 100644 (file)
--- a/src/doc/src/reference/manifest.md
+++ b/src/doc/src/reference/manifest.md
@@ -406,6 +406,9 @@ allowed to be published to.
 publish = ["some-registry-name"]
 ```
 
+If publish array contains a single registry, `cargo publish` command will use
+it when `--registry` flag is not specified.
+
 <a id="the-metadata-table-optional"></a>
 #### The `metadata` table