get rid of multi-line inputs; use textwrap.wrap automatically

Author: ankona

src/dotenv/main.py

@@ -5,6 +5,7 @@
 import shutil
 import sys
 import tempfile
+import textwrap
 from collections import OrderedDict
 from contextlib import contextmanager
 from typing import IO, Dict, Iterable, Iterator, Mapping, Optional, Tuple, Union
@@ -419,13 +420,14 @@ def set_header(
             logger.info("Ignoring empty header.")
             return False, header
 
-        header = header.strip()
-        lines = header.split("\n")
+        header = header.replace("\n", " ")
+        lines = textwrap.wrap(header, width=60)
         for i, line in enumerate(lines):
-            if not line.startswith("# "):
-                lines[i] = f"# {line}"
-        header = "\n".join(lines)
+            lines[i] = f"# {line}\n"
+        header = "".join(lines)
+        dest.write(header)
+
         text = "".join(atom for atom in source.readlines() if not atom.startswith("#"))
-        dest.write(f"{header}\n{text}\n")
+        dest.write(f"{text}\n")
 
     return True, header

tests/test_main.py

@@ -419,17 +419,17 @@ def test_set_header_empty(dotenv_path, header):
 @pytest.mark.parametrize(
     "new_header, expected, expected_header, old_header, content",
     [
-        ("# header only", True, "# header only", "", ""),
-        ("# single-line header", True, "# single-line header", "", "a=b\nc=d"),
-        ("# multi-line\n# header", True, "# multi-line\n# header", "", "a=b\nc=d"),
+        ("single-line input", True, "# single-line input\n", "", "a=b\nc=d"),
+        ("multi-line\ninput", True, "# multi-line input\n", "", "a=b\nc=d"),
+        ("new header", True, "# new header\n", "# old header", "a=b\nc=d"),
         (
-            "Single-line, no comment header",
+            " ".join("x" * 57 for _ in range(2)),
             True,
-            "# Single-line, no comment header",
+            "".join(f"# {'x' * 57}\n" for _ in range(2)),
             "",
             "a=b",
         ),
-        ("# New header", True, "# New header", "# Old header", "a=b\nc=d"),
+        # ("# New header", True, "# New header", "# Old header", "a=b\nc=d"),
     ],
 )
 def test_set_header(