refactor!(cli): make dry run a flag

Previously this had to be specified after the versions, but this was
undesired behavior.

src/cli.rs

@@ -6,8 +6,9 @@ use std::path::PathBuf;
 pub struct Args {
     #[clap(short, long)]
     pub config_file: Option<PathBuf>,
+    #[clap(short, long)]
+    pub dry_run: bool,
+
     pub old_version: String,
     pub new_version: String,
-
-    pub dry_run: bool,
 }