--override-input: Imply --no-write-lock-file

Fixes #3779.

src/libcmd/installables.cc

@@ -111,10 +111,11 @@ MixFlakeOptions::MixFlakeOptions()
 
     addFlag({
         .longName = "override-input",
-        .description = "Override a specific flake input (e.g. `dwarffs/nixpkgs`).",
+        .description = "Override a specific flake input (e.g. `dwarffs/nixpkgs`). This implies `--no-write-lock-file`.",
         .category = category,
         .labels = {"input-path", "flake-url"},
         .handler = {[&](std::string inputPath, std::string flakeRef) {
+            lockFlags.writeLockFile = false;
             lockFlags.inputOverrides.insert_or_assign(
                 flake::parseInputPath(inputPath),
                 parseFlakeRef(flakeRef, absPath(".")));

src/nix/flake.cc

@@ -110,6 +110,7 @@ struct CmdFlakeUpdate : FlakeCommand
         removeFlag("recreate-lock-file");
         removeFlag("update-input");
         removeFlag("no-update-lock-file");
+        removeFlag("no-write-lock-file");
     }
 
     std::string doc() override
@@ -124,6 +125,7 @@ struct CmdFlakeUpdate : FlakeCommand
         settings.tarballTtl = 0;
 
         lockFlags.recreateLockFile = true;
+        lockFlags.writeLockFile = true;
 
         lockFlake();
     }
@@ -136,6 +138,12 @@ struct CmdFlakeLock : FlakeCommand
         return "create missing lock file entries";
     }
 
+    CmdFlakeLock()
+    {
+        /* Remove flags that don't make sense. */
+        removeFlag("no-write-lock-file");
+    }
+
     std::string doc() override
     {
         return
@@ -147,6 +155,8 @@ struct CmdFlakeLock : FlakeCommand
     {
         settings.tarballTtl = 0;
 
+        lockFlags.writeLockFile = true;
+
         lockFlake();
     }
 };