diff --git a/src/bootstrap/src/core/build_steps/format.rs b/src/bootstrap/src/core/build_steps/format.rs
index 0e260e69c85a..86f1d925f73d 100644
--- a/src/bootstrap/src/core/build_steps/format.rs
+++ b/src/bootstrap/src/core/build_steps/format.rs
@@ -89,7 +89,7 @@ fn get_modified_rs_files(build: &Builder<'_>) -> Result<Option<Vec<String>>, Str
         return Ok(None);
     }
 
-    get_git_modified_files(Some(&build.config.src), &vec!["rs"])
+    get_git_modified_files(&build.config.git_config(), Some(&build.config.src), &vec!["rs"])
 }
 
 #[derive(serde_derive::Deserialize)]
diff --git a/src/bootstrap/src/core/build_steps/llvm.rs b/src/bootstrap/src/core/build_steps/llvm.rs
index 24351118a5aa..53a64e2b3fcc 100644
--- a/src/bootstrap/src/core/build_steps/llvm.rs
+++ b/src/bootstrap/src/core/build_steps/llvm.rs
@@ -132,8 +132,8 @@ pub(crate) fn detect_llvm_sha(config: &Config, is_git: bool) -> String {
         // walk back further to the last bors merge commit that actually changed LLVM. The first
         // step will fail on CI because only the `auto` branch exists; we just fall back to `HEAD`
         // in that case.
-        let closest_upstream =
-            get_git_merge_base(Some(&config.src)).unwrap_or_else(|_| "HEAD".into());
+        let closest_upstream = get_git_merge_base(&config.git_config(), Some(&config.src))
+            .unwrap_or_else(|_| "HEAD".into());
         let mut rev_list = config.git();
         rev_list.args(&[
             PathBuf::from("rev-list"),
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 5b5334b0a557..d3345f2d2a11 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -30,6 +30,7 @@ use serde::{Deserialize, Deserializer};
 use serde_derive::Deserialize;
 
 pub use crate::core::config::flags::Subcommand;
+use build_helper::git::GitConfig;
 
 macro_rules! check_ci_llvm {
     ($name:expr) => {
@@ -318,6 +319,7 @@ pub struct Stage0Config {
     pub artifacts_server: String,
     pub artifacts_with_llvm_assertions_server: String,
     pub git_merge_commit_email: String,
+    pub github_repository: String,
     pub nightly_branch: String,
 }
 #[derive(Default, Deserialize, Clone)]
@@ -2005,6 +2007,13 @@ impl Config {
         self.rust_codegen_backends.get(0).cloned()
     }
 
+    pub fn git_config(&self) -> GitConfig<'_> {
+        GitConfig {
+            github_repository: &self.stage0_metadata.config.github_repository,
+            nightly_branch: &self.stage0_metadata.config.nightly_branch,
+        }
+    }
+
     pub fn check_build_rustc_version(&self, rustc_path: &str) {
         if self.dry_run() {
             return;
diff --git a/src/stage0.json b/src/stage0.json
index 32dc8a2f83c6..8e6c43dc46d4 100644
--- a/src/stage0.json
+++ b/src/stage0.json
@@ -4,6 +4,7 @@
     "artifacts_server": "https://ci-artifacts.rust-lang.org/rustc-builds",
     "artifacts_with_llvm_assertions_server": "https://ci-artifacts.rust-lang.org/rustc-builds-alt",
     "git_merge_commit_email": "bors@rust-lang.org",
+    "github_repository": "rust-lang/rust",
     "nightly_branch": "master"
   },
   "__comments": [
diff --git a/src/tools/build_helper/src/git.rs b/src/tools/build_helper/src/git.rs
index f20b7a2b4d72..66f694dc919d 100644
--- a/src/tools/build_helper/src/git.rs
+++ b/src/tools/build_helper/src/git.rs
@@ -1,6 +1,11 @@
 use std::process::Stdio;
 use std::{path::Path, process::Command};
 
+pub struct GitConfig<'a> {
+    pub github_repository: &'a str,
+    pub nightly_branch: &'a str,
+}
+
 /// Runs a command and returns the output
 fn output_result(cmd: &mut Command) -> Result<String, String> {
     let output = match cmd.stderr(Stdio::inherit()).output() {
@@ -27,7 +32,10 @@ fn output_result(cmd: &mut Command) -> Result<String, String> {
 /// upstream        https://github.com/rust-lang/rust (fetch)
 /// upstream        https://github.com/rust-lang/rust (push)
 /// ```
-pub fn get_rust_lang_rust_remote(git_dir: Option<&Path>) -> Result<String, String> {
+pub fn get_rust_lang_rust_remote(
+    config: &GitConfig<'_>,
+    git_dir: Option<&Path>,
+) -> Result<String, String> {
     let mut git = Command::new("git");
     if let Some(git_dir) = git_dir {
         git.current_dir(git_dir);
@@ -37,8 +45,8 @@ pub fn get_rust_lang_rust_remote(git_dir: Option<&Path>) -> Result<String, Strin
 
     let rust_lang_remote = stdout
         .lines()
-        .find(|remote| remote.contains("rust-lang"))
-        .ok_or_else(|| "rust-lang/rust remote not found".to_owned())?;
+        .find(|remote| remote.contains(config.github_repository))
+        .ok_or_else(|| format!("{} remote not found", config.github_repository))?;
 
     let remote_name =
         rust_lang_remote.split('.').nth(1).ok_or_else(|| "remote name not found".to_owned())?;
@@ -76,9 +84,13 @@ pub fn rev_exists(rev: &str, git_dir: Option<&Path>) -> Result<bool, String> {
 /// This could be because the user is updating their forked master branch using the GitHub UI
 /// and therefore doesn't need an upstream master branch checked out.
 /// We will then fall back to origin/master in the hope that at least this exists.
-pub fn updated_master_branch(git_dir: Option<&Path>) -> Result<String, String> {
-    let upstream_remote = get_rust_lang_rust_remote(git_dir)?;
-    for upstream_master in [format!("{upstream_remote}/master"), format!("origin/master")] {
+pub fn updated_master_branch(
+    config: &GitConfig<'_>,
+    git_dir: Option<&Path>,
+) -> Result<String, String> {
+    let upstream_remote = get_rust_lang_rust_remote(config, git_dir)?;
+    let branch = config.nightly_branch;
+    for upstream_master in [format!("{upstream_remote}/{branch}"), format!("origin/{branch}")] {
         if rev_exists(&upstream_master, git_dir)? {
             return Ok(upstream_master);
         }
@@ -87,8 +99,11 @@ pub fn updated_master_branch(git_dir: Option<&Path>) -> Result<String, String> {
     Err(format!("Cannot find any suitable upstream master branch"))
 }
 
-pub fn get_git_merge_base(git_dir: Option<&Path>) -> Result<String, String> {
-    let updated_master = updated_master_branch(git_dir)?;
+pub fn get_git_merge_base(
+    config: &GitConfig<'_>,
+    git_dir: Option<&Path>,
+) -> Result<String, String> {
+    let updated_master = updated_master_branch(config, git_dir)?;
     let mut git = Command::new("git");
     if let Some(git_dir) = git_dir {
         git.current_dir(git_dir);
@@ -100,10 +115,11 @@ pub fn get_git_merge_base(git_dir: Option<&Path>) -> Result<String, String> {
 /// The `extensions` parameter can be used to filter the files by their extension.
 /// If `extensions` is empty, all files will be returned.
 pub fn get_git_modified_files(
+    config: &GitConfig<'_>,
     git_dir: Option<&Path>,
     extensions: &Vec<&str>,
 ) -> Result<Option<Vec<String>>, String> {
-    let merge_base = get_git_merge_base(git_dir)?;
+    let merge_base = get_git_merge_base(config, git_dir)?;
 
     let mut git = Command::new("git");
     if let Some(git_dir) = git_dir {
@@ -122,8 +138,11 @@ pub fn get_git_modified_files(
 }
 
 /// Returns the files that haven't been added to git yet.
-pub fn get_git_untracked_files(git_dir: Option<&Path>) -> Result<Option<Vec<String>>, String> {
-    let Ok(_updated_master) = updated_master_branch(git_dir) else {
+pub fn get_git_untracked_files(
+    config: &GitConfig<'_>,
+    git_dir: Option<&Path>,
+) -> Result<Option<Vec<String>>, String> {
+    let Ok(_updated_master) = updated_master_branch(config, git_dir) else {
         return Ok(None);
     };
     let mut git = Command::new("git");
diff --git a/src/tools/compiletest/src/common.rs b/src/tools/compiletest/src/common.rs
index 0e1bf0c6c2dc..cd9cf748aff0 100644
--- a/src/tools/compiletest/src/common.rs
+++ b/src/tools/compiletest/src/common.rs
@@ -8,6 +8,7 @@ use std::process::Command;
 use std::str::FromStr;
 
 use crate::util::{add_dylib_path, PathBufExt};
+use build_helper::git::GitConfig;
 use lazycell::AtomicLazyCell;
 use serde::de::{Deserialize, Deserializer, Error as _};
 use std::collections::{HashMap, HashSet};
@@ -370,6 +371,10 @@ pub struct Config {
     pub target_cfgs: AtomicLazyCell<TargetCfgs>,
 
     pub nocapture: bool,
+
+    // Needed both to construct build_helper::git::GitConfig
+    pub github_repository: String,
+    pub nightly_branch: String,
 }
 
 impl Config {
@@ -441,6 +446,13 @@ impl Config {
         ];
         ASM_SUPPORTED_ARCHS.contains(&self.target_cfg().arch.as_str())
     }
+
+    pub fn git_config(&self) -> GitConfig<'_> {
+        GitConfig {
+            github_repository: &self.github_repository,
+            nightly_branch: &self.nightly_branch,
+        }
+    }
 }
 
 #[derive(Debug, Clone)]
diff --git a/src/tools/compiletest/src/header/tests.rs b/src/tools/compiletest/src/header/tests.rs
index 2fd80b52ceee..1c89f8ba7639 100644
--- a/src/tools/compiletest/src/header/tests.rs
+++ b/src/tools/compiletest/src/header/tests.rs
@@ -126,6 +126,8 @@ impl ConfigBuilder {
             self.host.as_deref().unwrap_or("x86_64-unknown-linux-gnu"),
             "--target",
             self.target.as_deref().unwrap_or("x86_64-unknown-linux-gnu"),
+            "--github-repository=",
+            "--nightly-branch=",
         ];
         let mut args: Vec<String> = args.iter().map(ToString::to_string).collect();
 
diff --git a/src/tools/compiletest/src/lib.rs b/src/tools/compiletest/src/lib.rs
index 619ff9b32211..52e7f4174f10 100644
--- a/src/tools/compiletest/src/lib.rs
+++ b/src/tools/compiletest/src/lib.rs
@@ -144,7 +144,9 @@ pub fn parse_config(args: Vec<String>) -> Config {
         .optflag("h", "help", "show this message")
         .reqopt("", "channel", "current Rust channel", "CHANNEL")
         .optflag("", "git-hash", "run tests which rely on commit version being compiled into the binaries")
-        .optopt("", "edition", "default Rust edition", "EDITION");
+        .optopt("", "edition", "default Rust edition", "EDITION")
+        .reqopt("", "github-repository", "name of the GitHub repository", "ORG/REPO")
+        .reqopt("", "nightly-branch", "name of the git branch for nightly", "BRANCH");
 
     let (argv0, args_) = args.split_first().unwrap();
     if args.len() == 1 || args[1] == "-h" || args[1] == "--help" {
@@ -307,6 +309,9 @@ pub fn parse_config(args: Vec<String>) -> Config {
         target_cfgs: AtomicLazyCell::new(),
 
         nocapture: matches.opt_present("nocapture"),
+
+        github_repository: matches.opt_str("github-repository").unwrap(),
+        nightly_branch: matches.opt_str("nightly-branch").unwrap(),
     }
 }
 
@@ -609,9 +614,10 @@ fn modified_tests(config: &Config, dir: &Path) -> Result<Vec<PathBuf>, String> {
         return Ok(vec![]);
     }
     let files =
-        get_git_modified_files(Some(dir), &vec!["rs", "stderr", "fixed"])?.unwrap_or(vec![]);
+        get_git_modified_files(&config.git_config(), Some(dir), &vec!["rs", "stderr", "fixed"])?
+            .unwrap_or(vec![]);
     // Add new test cases to the list, it will be convenient in daily development.
-    let untracked_files = get_git_untracked_files(None)?.unwrap_or(vec![]);
+    let untracked_files = get_git_untracked_files(&config.git_config(), None)?.unwrap_or(vec![]);
 
     let all_paths = [&files[..], &untracked_files[..]].concat();
     let full_paths = {