_git_check_output_lines() now hardcodes Git binary

No need to give the Git binary name as the first command line element
in `["git", ...]`.

src/darker/git.py

@@ -37,7 +37,7 @@ def git_get_content_at_revision(path: Path, revision: str, cwd: Path) -> List[st
     """
     if revision == WORKTREE:
         return (cwd / path).read_text("utf-8").splitlines()
-    cmd = ["git", "show", f"{revision}:./{path}"]
+    cmd = ["show", f"{revision}:./{path}"]
     logger.debug("[%s]$ %s", cwd, " ".join(cmd))
     try:
         return _git_check_output_lines(cmd, cwd, exit_on_error=False)
@@ -110,7 +110,7 @@ def _git_check_output_lines(
     """Log command line, run Git, split stdout to lines, exit with 123 on error"""
     logger.debug("[%s]$ %s", cwd, " ".join(cmd))
     try:
-        return check_output(cmd, cwd=str(cwd)).decode("utf-8").splitlines()
+        return check_output(["git"] + cmd, cwd=str(cwd)).decode("utf-8").splitlines()
     except CalledProcessError as exc_info:
         if exc_info.returncode == 128 and exit_on_error:
             # Bad revision or another Git failure. Follow Black's example and return the
@@ -139,12 +139,11 @@ def git_get_modified_files(
     str_paths = [str(path) for path in relative_paths]
     if revrange.use_common_ancestor:
         rev2 = "HEAD" if revrange.rev2 == WORKTREE else revrange.rev2
-        merge_base_cmd = ["git", "merge-base", revrange.rev1, rev2]
+        merge_base_cmd = ["merge-base", revrange.rev1, rev2]
         rev1 = _git_check_output_lines(merge_base_cmd, cwd)[0]
     else:
         rev1 = revrange.rev1
     diff_cmd = [
-        "git",
         "diff",
         "--name-only",
         "--relative",
@@ -158,7 +157,6 @@ def git_get_modified_files(
     lines = _git_check_output_lines(diff_cmd, cwd)
     if revrange.rev2 == WORKTREE:
         ls_files_cmd = [
-            "git",
             "ls-files",
             "--others",
             "--exclude-standard",