refactor merge base logic and fix x fmt

src/bootstrap/src/core/build_steps/compile.rs

@@ -15,6 +15,7 @@ use std::path::{Path, PathBuf};
 use std::process::Stdio;
 use std::{env, fs, str};
 
+use build_helper::git::get_closest_merge_commit;
 use serde_derive::Deserialize;
 
 use crate::core::build_steps::tool::SourceType;
@@ -26,8 +27,7 @@ use crate::core::builder::{
 use crate::core::config::{DebuginfoLevel, LlvmLibunwind, RustcLto, TargetSelection};
 use crate::utils::exec::command;
 use crate::utils::helpers::{
-    self, exe, get_clang_cl_resource_dir, get_closest_merge_base_commit, is_debug_info, is_dylib,
-    symlink_dir, t, up_to_date,
+    self, exe, get_clang_cl_resource_dir, is_debug_info, is_dylib, symlink_dir, t, up_to_date,
 };
 use crate::{CLang, Compiler, DependencyType, GitRepo, Mode, LLVM_TOOLS};
 
@@ -127,13 +127,9 @@ impl Step for Std {
         // the `rust.download-rustc=true` option.
         let force_recompile =
             if builder.rust_info().is_managed_git_subrepository() && builder.download_rustc() {
-                let closest_merge_commit = get_closest_merge_base_commit(
-                    Some(&builder.src),
-                    &builder.config.git_config(),
-                    &builder.config.stage0_metadata.config.git_merge_commit_email,
-                    &[],
-                )
-                .unwrap();
+                let closest_merge_commit =
+                    get_closest_merge_commit(Some(&builder.src), &builder.config.git_config(), &[])
+                        .unwrap();
 
                 // Check if `library` has changes (returns false otherwise)
                 !t!(helpers::git(Some(&builder.src))

src/bootstrap/src/core/build_steps/format.rs

@@ -200,6 +200,11 @@ pub fn format(build: &Builder<'_>, check: bool, all: bool, paths: &[PathBuf]) {
                 adjective = Some("modified");
                 match get_modified_rs_files(build) {
                     Ok(Some(files)) => {
+                        if files.is_empty() {
+                            println!("fmt info: No modified files detected for formatting.");
+                            return;
+                        }
+
                         for file in files {
                             override_builder.add(&format!("/{file}")).expect(&file);
                         }

src/bootstrap/src/core/build_steps/llvm.rs

@@ -16,6 +16,7 @@ use std::sync::OnceLock;
 use std::{env, io};
 
 use build_helper::ci::CiEnv;
+use build_helper::git::get_closest_merge_commit;
 
 use crate::core::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::core::config::{Config, TargetSelection};
@@ -153,10 +154,9 @@ pub fn prebuilt_llvm_config(builder: &Builder<'_>, target: TargetSelection) -> L
 /// This retrieves the LLVM sha we *want* to use, according to git history.
 pub(crate) fn detect_llvm_sha(config: &Config, is_git: bool) -> String {
     let llvm_sha = if is_git {
-        helpers::get_closest_merge_base_commit(
+        get_closest_merge_commit(
             Some(&config.src),
             &config.git_config(),
-            &config.stage0_metadata.config.git_merge_commit_email,
             &[
                 config.src.join("src/llvm-project"),
                 config.src.join("src/bootstrap/download-ci-llvm-stamp"),

src/bootstrap/src/core/build_steps/suggest.rs

@@ -17,6 +17,7 @@ pub fn suggest(builder: &Builder<'_>, run: bool) {
         .tool_cmd(Tool::SuggestTests)
         .env("SUGGEST_TESTS_GIT_REPOSITORY", git_config.git_repository)
         .env("SUGGEST_TESTS_NIGHTLY_BRANCH", git_config.nightly_branch)
+        .env("SUGGEST_TESTS_MERGE_COMMIT_EMAIL", git_config.git_merge_commit_email)
         .run_capture_stdout(builder)
         .stdout();
 

src/bootstrap/src/core/build_steps/test.rs

@@ -2098,6 +2098,7 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
         let git_config = builder.config.git_config();
         cmd.arg("--git-repository").arg(git_config.git_repository);
         cmd.arg("--nightly-branch").arg(git_config.nightly_branch);
+        cmd.arg("--git-merge-commit-email").arg(git_config.git_merge_commit_email);
         cmd.force_coloring_in_ci();
 
         #[cfg(feature = "build-metrics")]

src/bootstrap/src/core/build_steps/tool.rs

@@ -1,14 +1,16 @@
 use std::path::PathBuf;
 use std::{env, fs};
 
+use build_helper::git::get_closest_merge_commit;
+
 use crate::core::build_steps::compile;
 use crate::core::build_steps::toolstate::ToolState;
 use crate::core::builder;
 use crate::core::builder::{Builder, Cargo as CargoCommand, RunConfig, ShouldRun, Step};
 use crate::core::config::TargetSelection;
 use crate::utils::channel::GitInfo;
 use crate::utils::exec::{command, BootstrapCommand};
-use crate::utils::helpers::{add_dylib_path, exe, get_closest_merge_base_commit, git, t};
+use crate::utils::helpers::{add_dylib_path, exe, git, t};
 use crate::{gha, Compiler, Kind, Mode};
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
@@ -576,10 +578,9 @@ impl Step for Rustdoc {
             && target_compiler.stage > 0
             && builder.rust_info().is_managed_git_subrepository()
         {
-            let commit = get_closest_merge_base_commit(
+            let commit = get_closest_merge_commit(
                 Some(&builder.config.src),
                 &builder.config.git_config(),
-                &builder.config.stage0_metadata.config.git_merge_commit_email,
                 &[],
             )
             .unwrap();

src/bootstrap/src/core/config/config.rs

@@ -14,7 +14,7 @@ use std::sync::OnceLock;
 use std::{cmp, env, fs};
 
 use build_helper::exit;
-use build_helper::git::{output_result, GitConfig};
+use build_helper::git::{get_closest_merge_commit, output_result, GitConfig};
 use serde::{Deserialize, Deserializer};
 use serde_derive::Deserialize;
 
@@ -24,7 +24,7 @@ pub use crate::core::config::flags::Subcommand;
 use crate::core::config::flags::{Color, Flags, Warnings};
 use crate::utils::cache::{Interned, INTERNER};
 use crate::utils::channel::{self, GitInfo};
-use crate::utils::helpers::{self, exe, get_closest_merge_base_commit, output, t};
+use crate::utils::helpers::{self, exe, output, t};
 
 macro_rules! check_ci_llvm {
     ($name:expr) => {
@@ -2509,6 +2509,7 @@ impl Config {
         GitConfig {
             git_repository: &self.stage0_metadata.config.git_repository,
             nightly_branch: &self.stage0_metadata.config.nightly_branch,
+            git_merge_commit_email: &self.stage0_metadata.config.git_merge_commit_email,
         }
     }
 
@@ -2685,13 +2686,7 @@ impl Config {
 
         // Look for a version to compare to based on the current commit.
         // Only commits merged by bors will have CI artifacts.
-        let commit = get_closest_merge_base_commit(
-            Some(&self.src),
-            &self.git_config(),
-            &self.stage0_metadata.config.git_merge_commit_email,
-            &[],
-        )
-        .unwrap();
+        let commit = get_closest_merge_commit(Some(&self.src), &self.git_config(), &[]).unwrap();
         if commit.is_empty() {
             println!("ERROR: could not find commit hash for downloading rustc");
             println!("HELP: maybe your repository history is too shallow?");
@@ -2782,13 +2777,7 @@ impl Config {
     ) -> Option<String> {
         // Look for a version to compare to based on the current commit.
         // Only commits merged by bors will have CI artifacts.
-        let commit = get_closest_merge_base_commit(
-            Some(&self.src),
-            &self.git_config(),
-            &self.stage0_metadata.config.git_merge_commit_email,
-            &[],
-        )
-        .unwrap();
+        let commit = get_closest_merge_commit(Some(&self.src), &self.git_config(), &[]).unwrap();
         if commit.is_empty() {
             println!("error: could not find commit hash for downloading components from CI");
             println!("help: maybe your repository history is too shallow?");

src/bootstrap/src/utils/helpers.rs

@@ -10,7 +10,6 @@ use std::sync::OnceLock;
 use std::time::{Instant, SystemTime, UNIX_EPOCH};
 use std::{env, fs, io, str};
 
-use build_helper::git::{get_git_merge_base, output_result, GitConfig};
 use build_helper::util::fail;
 
 use crate::core::builder::Builder;
@@ -523,28 +522,6 @@ pub fn git(source_dir: Option<&Path>) -> BootstrapCommand {
     git
 }
 
-/// Returns the closest commit available from upstream for the given `author` and `target_paths`.
-///
-/// If it fails to find the commit from upstream using `git merge-base`, fallbacks to HEAD.
-pub fn get_closest_merge_base_commit(
-    source_dir: Option<&Path>,
-    config: &GitConfig<'_>,
-    author: &str,
-    target_paths: &[PathBuf],
-) -> Result<String, String> {
-    let mut git = git(source_dir);
-
-    let merge_base = get_git_merge_base(config, source_dir).unwrap_or_else(|_| "HEAD".into());
-
-    git.args(["rev-list", &format!("--author={author}"), "-n1", "--first-parent", &merge_base]);
-
-    if !target_paths.is_empty() {
-        git.arg("--").args(target_paths);
-    }
-
-    Ok(output_result(git.as_command_mut())?.trim().to_owned())
-}
-
 /// Sets the file times for a given file at `path`.
 pub fn set_file_times<P: AsRef<Path>>(path: P, times: fs::FileTimes) -> io::Result<()> {
     // Windows requires file to be writable to modify file times. But on Linux CI the file does not

src/tools/build_helper/src/git.rs

@@ -1,9 +1,10 @@
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 
 pub struct GitConfig<'a> {
     pub git_repository: &'a str,
     pub nightly_branch: &'a str,
+    pub git_merge_commit_email: &'a str,
 }
 
 /// Runs a command and returns the output
@@ -95,7 +96,11 @@ pub fn updated_master_branch(
     Err("Cannot find any suitable upstream master branch".to_owned())
 }
 
-pub fn get_git_merge_base(
+/// Finds the nearest merge commit by comparing the local `HEAD` with the upstream branch's state.
+/// To work correctly, the upstream remote must be properly configured using `git remote add <name> <url>`.
+/// In most cases `get_closest_merge_commit` is the function you are looking for as it doesn't require remote
+/// to be configured.
+fn git_upstream_merge_base(
     config: &GitConfig<'_>,
     git_dir: Option<&Path>,
 ) -> Result<String, String> {
@@ -107,6 +112,38 @@ pub fn get_git_merge_base(
     Ok(output_result(git.arg("merge-base").arg(&updated_master).arg("HEAD"))?.trim().to_owned())
 }
 
+/// Searches for the nearest merge commit in the repository that also exists upstream.
+///
+/// If it fails to find the upstream remote, it then looks for the most recent commit made
+/// by the merge bot by matching the author's email address with the merge bot's email.
+pub fn get_closest_merge_commit(
+    git_dir: Option<&Path>,
+    config: &GitConfig<'_>,
+    target_paths: &[PathBuf],
+) -> Result<String, String> {
+    let mut git = Command::new("git");
+
+    if let Some(git_dir) = git_dir {
+        git.current_dir(git_dir);
+    }
+
+    let merge_base = git_upstream_merge_base(config, git_dir).unwrap_or_else(|_| "HEAD".into());
+
+    git.args([
+        "rev-list",
+        &format!("--author={}", config.git_merge_commit_email),
+        "-n1",
+        "--first-parent",
+        &merge_base,
+    ]);
+
+    if !target_paths.is_empty() {
+        git.arg("--").args(target_paths);
+    }
+
+    Ok(output_result(&mut git)?.trim().to_owned())
+}
+
 /// Returns the files that have been modified in the current branch compared to the master branch.
 /// The `extensions` parameter can be used to filter the files by their extension.
 /// Does not include removed files.
@@ -116,7 +153,7 @@ pub fn get_git_modified_files(
     git_dir: Option<&Path>,
     extensions: &[&str],
 ) -> Result<Option<Vec<String>>, String> {
-    let merge_base = get_git_merge_base(config, git_dir)?;
+    let merge_base = get_closest_merge_commit(git_dir, config, &[])?;
 
     let mut git = Command::new("git");
     if let Some(git_dir) = git_dir {

src/tools/compiletest/src/common.rs

@@ -384,6 +384,7 @@ pub struct Config {
     // Needed both to construct build_helper::git::GitConfig
     pub git_repository: String,
     pub nightly_branch: String,
+    pub git_merge_commit_email: String,
 
     /// True if the profiler runtime is enabled for this target.
     /// Used by the "needs-profiler-support" header in test files.
@@ -461,7 +462,11 @@ impl Config {
     }
 
     pub fn git_config(&self) -> GitConfig<'_> {
-        GitConfig { git_repository: &self.git_repository, nightly_branch: &self.nightly_branch }
+        GitConfig {
+            git_repository: &self.git_repository,
+            nightly_branch: &self.nightly_branch,
+            git_merge_commit_email: &self.git_merge_commit_email,
+        }
     }
 }
 

src/tools/compiletest/src/header/tests.rs

@@ -148,6 +148,7 @@ impl ConfigBuilder {
             self.target.as_deref().unwrap_or("x86_64-unknown-linux-gnu"),
             "--git-repository=",
             "--nightly-branch=",
+            "--git-merge-commit-email=",
         ];
         let mut args: Vec<String> = args.iter().map(ToString::to_string).collect();
 

src/tools/compiletest/src/lib.rs

@@ -163,7 +163,13 @@ pub fn parse_config(args: Vec<String>) -> Config {
         )
         .optopt("", "edition", "default Rust edition", "EDITION")
         .reqopt("", "git-repository", "name of the git repository", "ORG/REPO")
-        .reqopt("", "nightly-branch", "name of the git branch for nightly", "BRANCH");
+        .reqopt("", "nightly-branch", "name of the git branch for nightly", "BRANCH")
+        .reqopt(
+            "",
+            "git-merge-commit-email",
+            "email address used for finding merge commits",
+            "EMAIL",
+        );
 
     let (argv0, args_) = args.split_first().unwrap();
     if args.len() == 1 || args[1] == "-h" || args[1] == "--help" {
@@ -346,6 +352,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
 
         git_repository: matches.opt_str("git-repository").unwrap(),
         nightly_branch: matches.opt_str("nightly-branch").unwrap(),
+        git_merge_commit_email: matches.opt_str("git-merge-commit-email").unwrap(),
 
         profiler_support: matches.opt_present("profiler-support"),
     }

src/tools/suggest-tests/src/main.rs

@@ -8,6 +8,7 @@ fn main() -> ExitCode {
         &GitConfig {
             git_repository: &env("SUGGEST_TESTS_GIT_REPOSITORY"),
             nightly_branch: &env("SUGGEST_TESTS_NIGHTLY_BRANCH"),
+            git_merge_commit_email: &env("SUGGEST_TESTS_MERGE_COMMIT_EMAIL"),
         },
         None,
         &Vec::new(),