Add option to set from stdin using railway variables

src/commands/variables.rs

@@ -34,6 +34,27 @@ pub struct Args {
     #[clap(long)]
     set: Vec<Variable>,
 
+    /// Read environment variable pairs from stdin.
+    ///
+    /// Each line should contain exactly one "{KEY}={VALUE}"" pair. Leading and trailing whitespace is trimmed.
+    /// Empty lines are ignored. If combined with --set, values from both sources are applied.
+    ///
+    /// Examples:
+    ///
+    ///     # Read a single variable from stdin
+    ///
+    ///     echo "FOO=bar" | railway variables --set-from-stdin
+    ///
+    ///     # Read multiple variables, one per line
+    ///
+    ///     printf "FOO=bar\nBAZ=qux\n" | railway variables --set-from-stdin
+    ///
+    ///     # Load variables from a .env file
+    ///
+    ///     cat .env | railway variables --set-from-stdin
+    #[clap(long, verbatim_doc_comment)]
+    set_from_stdin: bool,
+
     /// Output in JSON format
     #[clap(long)]
     json: bool,
@@ -43,7 +64,7 @@ pub struct Args {
     skip_deploys: bool,
 }
 
-pub async fn command(args: Args) -> Result<()> {
+pub async fn command(mut args: Args) -> Result<()> {
     let configs = Configs::new()?;
     let client = GQLClient::new_authorized(&configs)?;
     let linked_project = configs.get_linked_project().await?;
@@ -74,6 +95,22 @@ pub async fn command(args: Args) -> Result<()> {
         _ => bail!(RailwayError::NoServiceLinked),
     };
 
+    if args.set_from_stdin {
+        let stdin = stdin();
+
+        if stdin.is_terminal() {
+            bail!("--set-from-stdin requires input from stdin (e.g., via pipe or redirect)");
+        }
+
+        for line in stdin.lock().lines() {
+            let line = line?;
+
+            if !line.trim().is_empty() {
+                args.set.push(line.trim().to_string());
+            }
+        }
+    }
+
     if !args.set.is_empty() {
         set_variables(
             args.set,