Minor fixes identified through shellcheck and other tools (#350)

* fix whitespace

* fix spelling

* fix whitespace

* unify headers of tests

* fix some issues in tests, identified by shellcheck

* fix bash completions

bash completion files are not supposed to be executable

* fix some issues identified by shellcheck

Co-authored-by: Ali Karbassi <ali@karbassi.com>

tests/t6080-completion-path.sh

@@ -1,5 +1,4 @@
 #!/bin/bash
-#
 
 test_description='Bash completion with different path functionality
 
@@ -28,8 +27,6 @@ _todo2()
 
 test_todo_custom_completion _todo2 'all todo2 contexts' 'todo2 list @' '@garden @outdoor @outside'
 
-
-
 # Remove the test environment's bin directory from the PATH, so that our test
 # executable must be launched with an explicit path.
 PATH=${PATH##"${PWD}/bin:"}