ansible-vault: add newline to the output of the 'encrypt_string' command (#79017)

* ansible-vault: add newline to the output of the 'encrypt_string' command

* Add comment with issue description and improve string joining

* Add changelog fragment

* Update changelogs/fragments/79017-ansible-vault-string-encryption-ending-with-newline.yml

Co-authored-by: Sviatoslav Sydorenko <wk.cvs.github@sydorenko.org.ua>

* Fixed some typos in changelog fragment

* Improve comment regarding newline character at the end of file

Co-authored-by: Sviatoslav Sydorenko <wk.cvs.github@sydorenko.org.ua>

Co-authored-by: Sviatoslav Sydorenko <wk.cvs.github@sydorenko.org.ua>

changelogs/fragments/79017-ansible-vault-string-encryption-ending-with-newline.yml

@@ -0,0 +1,6 @@
+bugfixes:
+  - >-
+    ansible-vault encrypt_string - started appending a line feed at the end of the encrypted string output. Missing newline
+    character caused problems identifying where the string ends in some shells (like bash) or accidentally copying an
+    extra trailing terminator symbol (e.g., zsh prints out a ``%`` sign to signal where the original output stops)
+    (https://github.com/ansible/ansible/issues/78932).

lib/ansible/cli/vault.py

@@ -384,6 +384,11 @@ class VaultCLI(CLI):
                 sys.stderr.write(err)
             b_outs.append(to_bytes(out))
 
+        # The output must end with a newline to play nice with terminal representation.
+        # Refs:
+        # * https://stackoverflow.com/a/729795/595220
+        # * https://github.com/ansible/ansible/issues/78932
+        b_outs.append(b'')
         self.editor.write_data(b'\n'.join(b_outs), context.CLIARGS['output_file'] or '-')
 
         if sys.stdout.isatty():