README.md: Config reference: arch

Reported-by: Mark Wooding <mdw@distorted.org.uk>
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/README.md b/README.md
index 02dede042dd2a7d85744f37c8570ca068018d49d..e9bd358d056f772b78b4d02ccfd602f52669629d 100644 (file)
--- a/README.md
+++ b/README.md
@@ -330,6 +330,16 @@ To control use of alternative `Cargo.lock` filename, use the section
  * `user`: The local username for `really` and `ssh`, or
    `<user>@<host>` for `ssh`.
 
+`[arch]`: Architecture convenience aliases
+------------------------------------------
+
+This is a map from archictecture aliases to full cargo architecture
+names.  The keys are the aliases; each entry should be a string, the
+cargo architecture name.
+
+Only keys starting with an ascii uppercase letter are relevant, since
+all other names are not looked up in this alias map.
+
 Running the command
 ===================