rebase -i: quick/inline reword

Currently, `rebase -i` allows modifying the commit titles in the list, and
the modified title is shown in the lists of previous and next commands, but
the changes are not saved. Currently, modifying just the titles of many
commits requires `reword`ing each one and separately and consecutively editing
each message, which is annoying when making small, repetitive edits, especially
since it requires double-checking each one separately. It would be much easier
if there were a mode where any changes to the commit titles in the list
modified the commits' titles. Maybe `git rebase -i --reword`?

Any thoughts, suggestions, questions, etc.?

FYI, I am using git version 2.20.1 on `Linux ghostwheel 4.19.0-8-amd64 #1 SMP
Debian 4.19.98-1 (2020-01-26) x86_64 GNU/Linux`.

Solomon Ucko

P.S. This is my first time posting here, so let me know if I accidentally
violated any rules, e.g. etiquette or formatting.