bootstrap: add the dist.compression-formats option

The option allows to add or remove compression formats used while
producing dist tarballs.

config.toml.example

@@ -669,3 +669,7 @@ changelog-seen = 2
 
 # Whether to allow failures when building tools
 #missing-tools = false
+
+# List of compression formats to use when generating dist tarballs. The list of
+# formats is provided to rust-installer, which must support all of them.
+#compression-formats = ["gz", "xz"]

src/bootstrap/config.rs

@@ -148,6 +148,7 @@ pub struct Config {
     pub dist_sign_folder: Option<PathBuf>,
     pub dist_upload_addr: Option<String>,
     pub dist_gpg_password_file: Option<PathBuf>,
+    pub dist_compression_formats: Option<Vec<String>>,
 
     // libstd features
     pub backtrace: bool, // support for RUST_BACKTRACE
@@ -438,6 +439,7 @@ struct Dist {
     upload_addr: Option<String>,
     src_tarball: Option<bool>,
     missing_tools: Option<bool>,
+    compression_formats: Option<Vec<String>>,
 }
 
 #[derive(Deserialize)]
@@ -936,6 +938,7 @@ impl Config {
             config.dist_sign_folder = t.sign_folder.map(PathBuf::from);
             config.dist_gpg_password_file = t.gpg_password_file.map(PathBuf::from);
             config.dist_upload_addr = t.upload_addr;
+            config.dist_compression_formats = t.compression_formats;
             set(&mut config.rust_dist_src, t.src_tarball);
             set(&mut config.missing_tools, t.missing_tools);
         }

src/bootstrap/configure.py

@@ -147,6 +147,8 @@ v("experimental-targets", "llvm.experimental-targets",
   "experimental LLVM targets to build")
 v("release-channel", "rust.channel", "the name of the release channel to build")
 v("release-description", "rust.description", "optional descriptive string for version output")
+v("dist-compression-formats", None,
+  "comma-separated list of compression formats to use")
 
 # Used on systems where "cc" is unavailable
 v("default-linker", "rust.default-linker", "the default linker")
@@ -349,6 +351,8 @@ for key in known_args:
     elif option.name == 'option-checking':
         # this was handled above
         pass
+    elif option.name == 'dist-compression-formats':
+        set('dist.compression-formats', value.split(','))
     else:
         raise RuntimeError("unhandled option {}".format(option.name))
 

src/bootstrap/tarball.rs

@@ -288,11 +288,25 @@ impl<'a> Tarball<'a> {
 
         build_cli(&self, &mut cmd);
         cmd.arg("--work-dir").arg(&self.temp_dir);
+        if let Some(formats) = &self.builder.config.dist_compression_formats {
+            assert!(!formats.is_empty(), "dist.compression-formats can't be empty");
+            cmd.arg("--compression-formats").arg(formats.join(","));
+        }
         self.builder.run(&mut cmd);
         if self.delete_temp_dir {
             t!(std::fs::remove_dir_all(&self.temp_dir));
         }
 
-        crate::dist::distdir(self.builder).join(format!("{}.tar.gz", package_name))
+        // Use either the first compression format defined, or "gz" as the default.
+        let ext = self
+            .builder
+            .config
+            .dist_compression_formats
+            .as_ref()
+            .and_then(|formats| formats.get(0))
+            .map(|s| s.as_str())
+            .unwrap_or("gz");
+
+        crate::dist::distdir(self.builder).join(format!("{}.tar.{}", package_name, ext))
     }
 }