lint: [move-only] Move util functions to util.rs

diff --git a/test/lint/test_runner/src/main.rs b/test/lint/test_runner/src/main.rs
index 171c9807..3a870b94 100644
--- a/test/lint/test_runner/src/main.rs
+++ b/test/lint/test_runner/src/main.rs
@@ -2,18 +2,17 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or https://opensource.org/license/mit/.
 
+mod util;
+
 use std::env;
 use std::fs::{self, File};
 use std::io::{ErrorKind, Read, Seek, SeekFrom};
-use std::path::PathBuf;
 use std::process::{Command, ExitCode, Stdio};
 
-/// A possible error returned by any of the linters.
-///
-/// The error string should explain the failure type and list all violations.
-type LintError = String;
-type LintResult = Result<(), LintError>;
-type LintFn = fn() -> LintResult;
+use util::{
+    check_output, commit_range, get_git_root, get_pathspecs_default_excludes, get_subtrees, git,
+    LintFn, LintResult,
+};
 
 struct Linter {
     pub description: &'static str,
@@ -157,76 +156,6 @@ fn parse_lint_args(args: &[String]) -> Vec<&'static Linter> {
     lint_values
 }
 
-/// Return the git command
-///
-/// Lint functions should use this command, so that only files tracked by git are considered and
-/// temporary and untracked files are ignored. For example, instead of 'grep', 'git grep' should be
-/// used.
-fn git() -> Command {
-    let mut git = Command::new("git");
-    git.arg("--no-pager");
-    git
-}
-
-/// Return stdout on success and a LintError on failure, when invalid UTF8 was detected or the
-/// command did not succeed.
-fn check_output(cmd: &mut std::process::Command) -> Result<String, LintError> {
-    let out = cmd.output().expect("command error");
-    if !out.status.success() {
-        return Err(String::from_utf8_lossy(&out.stderr).to_string());
-    }
-    Ok(String::from_utf8(out.stdout)
-        .map_err(|e| {
-            format!("All path names, source code, messages, and output must be valid UTF8!\n{e}")
-        })?
-        .trim()
-        .to_string())
-}
-
-/// Return the git root as utf8, or panic
-fn get_git_root() -> PathBuf {
-    PathBuf::from(check_output(git().args(["rev-parse", "--show-toplevel"])).unwrap())
-}
-
-/// Return the commit range, or panic
-fn commit_range() -> String {
-    // Use the env var, if set. E.g. COMMIT_RANGE='HEAD~n..HEAD' for the last 'n' commits.
-    env::var("COMMIT_RANGE").unwrap_or_else(|_| {
-        // Otherwise, assume that a merge commit exists. This merge commit is assumed
-        // to be the base, after which linting will be done. If the merge commit is
-        // HEAD, the range will be empty.
-        format!(
-            "{}..HEAD",
-            check_output(git().args(["rev-list", "--max-count=1", "--merges", "HEAD"]))
-                .expect("check_output failed")
-        )
-    })
-}
-
-/// Return all subtree paths
-fn get_subtrees() -> Vec<&'static str> {
-    // Keep in sync with [test/lint/README.md#git-subtree-checksh]
-    vec![
-        "src/crc32c",
-        "src/crypto/ctaes",
-        "src/ipc/libmultiprocess",
-        "src/leveldb",
-        "src/minisketch",
-        "src/secp256k1",
-    ]
-}
-
-/// Return the pathspecs to exclude by default
-fn get_pathspecs_default_excludes() -> Vec<String> {
-    get_subtrees()
-        .iter()
-        .chain(&[
-            "doc/release-notes/release-notes-*", // archived notes
-        ])
-        .map(|s| format!(":(exclude){s}"))
-        .collect()
-}
-
 fn lint_subtree() -> LintResult {
     // This only checks that the trees are pure subtrees, it is not doing a full
     // check with -r to not have to fetch all the remotes.
diff --git a/test/lint/test_runner/src/util.rs b/test/lint/test_runner/src/util.rs
new file mode 100644
index 00000000..11e332e4
--- /dev/null
+++ b/test/lint/test_runner/src/util.rs
@@ -0,0 +1,84 @@
+// Copyright (c) The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://opensource.org/license/mit/.
+
+use std::env;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A possible error returned by any of the linters.
+///
+/// The error string should explain the failure type and list all violations.
+pub type LintError = String;
+pub type LintResult = Result<(), LintError>;
+pub type LintFn = fn() -> LintResult;
+
+/// Return the git command
+///
+/// Lint functions should use this command, so that only files tracked by git are considered and
+/// temporary and untracked files are ignored. For example, instead of 'grep', 'git grep' should be
+/// used.
+pub fn git() -> Command {
+    let mut git = Command::new("git");
+    git.arg("--no-pager");
+    git
+}
+
+/// Return stdout on success and a LintError on failure, when invalid UTF8 was detected or the
+/// command did not succeed.
+pub fn check_output(cmd: &mut Command) -> Result<String, LintError> {
+    let out = cmd.output().expect("command error");
+    if !out.status.success() {
+        return Err(String::from_utf8_lossy(&out.stderr).to_string());
+    }
+    Ok(String::from_utf8(out.stdout)
+        .map_err(|e| {
+            format!("All path names, source code, messages, and output must be valid UTF8!\n{e}")
+        })?
+        .trim()
+        .to_string())
+}
+
+/// Return the git root as utf8, or panic
+pub fn get_git_root() -> PathBuf {
+    PathBuf::from(check_output(git().args(["rev-parse", "--show-toplevel"])).unwrap())
+}
+
+/// Return the commit range, or panic
+pub fn commit_range() -> String {
+    // Use the env var, if set. E.g. COMMIT_RANGE='HEAD~n..HEAD' for the last 'n' commits.
+    env::var("COMMIT_RANGE").unwrap_or_else(|_| {
+        // Otherwise, assume that a merge commit exists. This merge commit is assumed
+        // to be the base, after which linting will be done. If the merge commit is
+        // HEAD, the range will be empty.
+        format!(
+            "{}..HEAD",
+            check_output(git().args(["rev-list", "--max-count=1", "--merges", "HEAD"]))
+                .expect("check_output failed")
+        )
+    })
+}
+
+/// Return all subtree paths
+pub fn get_subtrees() -> Vec<&'static str> {
+    // Keep in sync with [test/lint/README.md#git-subtree-checksh]
+    vec![
+        "src/crc32c",
+        "src/crypto/ctaes",
+        "src/ipc/libmultiprocess",
+        "src/leveldb",
+        "src/minisketch",
+        "src/secp256k1",
+    ]
+}
+
+/// Return the pathspecs to exclude by default
+pub fn get_pathspecs_default_excludes() -> Vec<String> {
+    get_subtrees()
+        .iter()
+        .chain(&[
+            "doc/release-notes/release-notes-*", // archived notes
+        ])
+        .map(|s| format!(":(exclude){s}"))
+        .collect()
+}