export NNN_PREFER_SELECTION to all plugins

plugins/README.md

@@ -212,6 +212,7 @@ When `nnn` executes a plugin, it does the following:
     3. `$3`: The picker mode output file (`-` for stdout) if `nnn` is executed as a file picker.
 - Sets the environment variable `NNN_PIPE` used to control `nnn` active directory.
 - Sets the environment variable `NNN_INCLUDE_HIDDEN` to `1` if hidden files are active, `0` otherwise.
+- Sets the environment variable `NNN_PREFER_SELECTION` to `1` if user prefers to use selection (see nnn's `-u` flag), `0` otherwise.
 - Exports the [special variables](https://github.com/jarun/nnn/wiki/Concepts#special-variables).
 
 Plugins can also read the `.selection` file in the config directory.

src/nnn.c

@@ -5174,6 +5174,7 @@ static void setexports(void)
 		}
 	}
 	setenv("NNN_INCLUDE_HIDDEN", xitoa(cfg.showhidden), 1);
+	setenv("NNN_PREFER_SELECTION", xitoa(cfg.prefersel), 1);
 }
 
 static void run_cmd_as_plugin(const char *file, uchar_t flags)