* lisp/mh-e/mh-thread.el (mh-thread-current-indentation-level)
(mh-thread-find-children): Fix off-by-one error by using
'mh-scan-field-from-start-offset' directly, as
'mh-thread-parse-scan-line' does. Previously, these functions would
incorrectly consider the "date note" column as part of the thread
indenting. Since that column is almost always a Space character, that
almost always worked.
(mh-thread-ancestor): Update caller.
* test/lisp/mh-e/mh-thread-tests.el: New unit tests for affected code.
* lisp/mh-e/mh-scan.el (mh-msg-num-width-to-column): Fix doc string typo.
