Prevent duplication and modification of shebang in shell scripts (#1208)

* Fix: Prevent duplication and modification of shebang

This changes the behavior when adding a header to a file which
previously had no copyright/license header. If the first line of the
file starts with a shebang (`#!`), the header is put below the first
line instead of above.

The previous approach was to include the shebang in the template, but
this caused the shebang to be duplicated as the template is prepended
without modifying the rest of the file. Since the template was chosen
based on the file extension, this could also cause a script with a `.sh`
extension and a `#!/bin/bash` shebang to now have a `#!/bin/sh` shebang,
potentially causing the script to be executed using a different shell.

* Change: Remove shebang from templates

Remove workaround of having the shebang in the template for shell
scripts as this is now handled within
`pontos/updateheader/updateheader.py`.

* Add: new test case for files starting with shebang

Author: wiegandm

pontos/updateheader/templates/AGPL-3.0-or-later/template.bash

@@ -1,4 +1,3 @@
-#!/bin/bash
 # SPDX-FileCopyrightText: <year> <company>
 #
 # SPDX-License-Identifier: AGPL-3.0-or-later

pontos/updateheader/templates/AGPL-3.0-or-later/template.sh

@@ -1,4 +1,3 @@
-#!/bin/sh
 # SPDX-FileCopyrightText: <year> <company>
 #
 # SPDX-License-Identifier: AGPL-3.0-or-later

pontos/updateheader/templates/GPL-2.0-or-later/template.bash

@@ -1,4 +1,3 @@
-#!/bin/bash
 # SPDX-FileCopyrightText: <year> <company>
 #
 # SPDX-License-Identifier: GPL-2.0-or-later

pontos/updateheader/templates/GPL-2.0-or-later/template.sh

@@ -1,4 +1,3 @@
-#!/bin/sh
 # SPDX-FileCopyrightText: <year> <company>
 #
 # SPDX-License-Identifier: GPL-2.0-or-later

pontos/updateheader/templates/GPL-3.0-or-later/template.bash

@@ -1,4 +1,3 @@
-#!/bin/bash
 # SPDX-FileCopyrightText: <year> <company>
 #
 # SPDX-License-Identifier: GPL-3.0-or-later

pontos/updateheader/templates/GPL-3.0-or-later/template.sh

@@ -1,4 +1,3 @@
-#!/bin/sh
 # SPDX-FileCopyrightText: <year> <company>
 #
 # SPDX-License-Identifier: GPL-3.0-or-later

pontos/updateheader/updateheader.py

@@ -191,9 +191,18 @@ def update_file(
                     )
                     if header:
                         fp.seek(0)  # back to beginning of file
-                        rest_of_file = fp.read()
-                        fp.seek(0)
-                        fp.write(header + "\n" + rest_of_file)
+                        first_line = fp.readline()
+
+                        # first line is a shebang, leave it
+                        if first_line.startswith("#!"):
+                            rest_of_file = fp.read()
+                            fp.seek(0)
+                            fp.write(first_line + header + "\n" + rest_of_file)
+                        else:
+                            rest_of_file = first_line + fp.read()
+                            fp.seek(0)
+                            fp.write(header + "\n" + rest_of_file)
+
                         print(f"{file}: Added license header.")
                         return
 

tests/updateheader/test_header.py

@@ -567,6 +567,34 @@ def test_cleanup_file_changed_company(self):
             new_content = tmp.read_text(encoding="utf-8")
             self.assertEqual(expected_content, new_content)
 
+    def test_handle_file_with_shebang(self):
+        test_content = """#!/bin/bash
+"""  # noqa: E501
+
+        expected_content = f"""#!/bin/bash
+# SPDX-FileCopyrightText: {str(datetime.datetime.now().year)} Greenbone AG
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+"""  # noqa: E501
+
+        company = "Greenbone AG"
+        year = str(datetime.datetime.now().year)
+        license_id = "GPL-3.0-or-later"
+
+        with temp_file(content=test_content, name="foo.sh") as tmp:
+
+            update_file(
+                tmp,
+                year,
+                license_id,
+                company,
+                cleanup=True,
+            )
+
+            new_content = tmp.read_text(encoding="utf-8")
+            self.assertEqual(expected_content, new_content)
+
 
 class ParseArgsTestCase(TestCase):
     def test_argparser_files(self):