Add --database-url to command line

sqlx-cli/README.md

@@ -17,7 +17,7 @@ $ cargo install --version=0.1.0-beta.1 sqlx-cli --no-default-features --features
 
 ### Usage
 
-All commands require `DATABASE_URL` to be set, either in the environment or in a `.env` file
+All commands require that a database url is provided. This can be done either with the `--database-url` command line option or by setting `DATABASE_URL`, either in the environment or in a `.env` file
 in the current working directory.
 
 `database` and `migrate` subcommands support only Postgres; MySQL and SQLite are TODO.

sqlx-cli/src/lib.rs

@@ -15,8 +15,11 @@ pub use crate::opt::Opt;
 pub async fn run(opt: Opt) -> anyhow::Result<()> {
     dotenv().ok();
 
-    let database_url = env::var("DATABASE_URL")
-        .map_err(|_| anyhow!("The DATABASE_URL environment variable must be set"))?;
+    let database_url = match opt.database_url {
+        Some(db_url) => db_url,
+        None => env::var("DATABASE_URL")
+            .map_err(|_| anyhow!("The DATABASE_URL environment variable must be set"))?,
+    };
 
     match opt.command {
         Command::Migrate(migrate) => match migrate.command {

sqlx-cli/src/opt.rs

@@ -4,6 +4,9 @@ use clap::Clap;
 pub struct Opt {
     #[clap(subcommand)]
     pub command: Command,
+
+    #[clap(short = "D", long)]
+    pub database_url: Option<String>,
 }
 
 #[derive(Clap, Debug)]