xtask: simplify env variables

Author: phip1611

xtask/Cargo.toml

@@ -7,7 +7,7 @@ edition.workspace = true
 
 [dependencies]
 anyhow = "1.0.51"
-clap = { version = "4.4.0", default-features = false, features = ["derive", "help", "usage", "std"] }
+clap = { version = "4.4.0", default-features = false, features = ["derive", "help", "usage", "std", "env"] }
 fatfs = { version = "0.3.6", default-features = false, features = ["alloc", "std"] }
 fs-err = "3.0.0"
 heck = "0.5.0"

xtask/src/opt.rs

@@ -187,15 +187,15 @@ pub struct QemuOpt {
     pub tpm: Option<TpmVersion>,
 
     /// Path of an OVMF code file.
-    #[clap(long, action)]
+    #[clap(long, action, env)]
     pub ovmf_code: Option<PathBuf>,
 
     /// Path of an OVMF vars file.
-    #[clap(long, action)]
+    #[clap(long, action, env)]
     pub ovmf_vars: Option<PathBuf>,
 
     /// Path of an OVMF shell application.
-    #[clap(long, action)]
+    #[clap(long, action, env)]
     pub ovmf_shell: Option<PathBuf>,
 
     /// Run an example instead of the main binary.

xtask/src/qemu.rs

@@ -26,15 +26,6 @@ const OVMF_PREBUILT_SOURCE: Source = Source::EDK2_STABLE202502_R2;
 /// Directory into which the prebuilts will be download (relative to the repo root).
 const OVMF_PREBUILT_DIR: &str = "target/ovmf";
 
-/// Environment variable for overriding the path of the OVMF code file.
-const ENV_VAR_OVMF_CODE: &str = "OVMF_CODE";
-
-/// Environment variable for overriding the path of the OVMF vars file.
-const ENV_VAR_OVMF_VARS: &str = "OVMF_VARS";
-
-/// Environment variable for overriding the path of the OVMF shell file.
-const ENV_VAR_OVMF_SHELL: &str = "OVMF_SHELL";
-
 impl From<UefiArch> for ovmf_prebuilt::Arch {
     fn from(arch: UefiArch) -> Self {
         match arch {
@@ -51,26 +42,18 @@ impl From<UefiArch> for ovmf_prebuilt::Arch {
 /// environment variable. If neither is present, returns `None`.
 fn get_user_provided_path(file_type: FileType, opt: &QemuOpt) -> Option<PathBuf> {
     let opt_path;
-    let var_name;
     match file_type {
         FileType::Code => {
             opt_path = &opt.ovmf_code;
-            var_name = ENV_VAR_OVMF_CODE;
         }
         FileType::Vars => {
             opt_path = &opt.ovmf_vars;
-            var_name = ENV_VAR_OVMF_VARS;
         }
         FileType::Shell => {
             opt_path = &opt.ovmf_shell;
-            var_name = ENV_VAR_OVMF_SHELL;
         }
     }
-    if let Some(path) = opt_path {
-        Some(path.clone())
-    } else {
-        env::var_os(var_name).map(PathBuf::from)
-    }
+    opt_path.clone()
 }
 
 struct OvmfPaths {