> It's a, assuming that those code lines are gone for good, i.e. the
> current code is not merely some transformation of those original
> lines.  The "annotate" (or "blame") command will not tell you, because
> it attributes whole lines; you need to look at the diffs between the
> last version that did have that code and the current code, and analyze
> that.

I know that annotate/blame is not enough. I do precisely what you are
suggesting: looking  at the diffs, that is why this it is so extensive, 🙃
 

> Btw, the "15-lines" rule is just an approximation: depending on what
> are those lines, it could be much more, or it could be slightly less.
> It's a judgment call, not a mechanistic line count.

I see, on that subject another question for the future: suppose I as a
maintainer receive a 2 lines patch for example

,----
| 
| diff --git a/elisp/matlab-emacs/matlab.el b/elisp/matlab-emacs/matlab.el
| index 63ce838..71b6ff0 100755
| --- a/elisp/matlab-emacs/matlab.el
| +++ b/elisp/matlab-emacs/matlab.el
| @@ -3731,6 +3731,6 @@ If ARG is nil, then highlighting is toggled."
|  			  post-command-hook)
|  		  -1 1)))
|      (if (> arg 0)
| -	(add-hook 'post-command-hook 'matlab-start-block-highlight-timer)
| -      (remove-hook 'post-command-hook 'matlab-start-block-highlight-timer))))
| +	(add-hook 'post-command-hook 'matlab-start-block-highlight-timer nil :local)
| +      (remove-hook 'post-command-hook 'matlab-start-block-highlight-timer :local))))
| 
`----

Since this is legally not significant, (I hope you agree): 

Should I commit this under my name (with reference in the log message to
the author), or should I commit that under the authors name?

Regards