nix copy: Rename --substitute to --substitute-on-destination

'--substitute' was being shadowed by the regular '--substitute' (the
short-hand for '--option substitute true').

Fixes #2983.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/nix/copy.cc b/src/nix/copy.cc
index 96bd453d87b4..12a9f9cd3372 100644
--- a/src/nix/copy.cc
+++ b/src/nix/copy.cc
@@ -36,7 +36,7 @@ struct CmdCopy : StorePathsCommand
             .set(&checkSigs, NoCheckSigs);
 
         mkFlag()
-            .longName("substitute")
+            .longName("substitute-on-destination")
             .shortName('s')
             .description("whether to try substitutes on the destination store (only supported by SSH)")
             .set(&substitute, Substitute);