Re: magic-mode-alist gets in the way

[Richard Stallman]

    I can't think of a good reason why the content should always take precedence
    over the file name.

In actual practice, that is normally what we want.  Whether on
theoretical grounds that must always be true is not the crucial
question.

      If a file "foo.html" starts with "#!/bin/sh" it makes
    perfect sense to edit it as an HTML file rather than a shell script.

magic-mode-alist is not involved in detecting interpreter lines, so
this doesn't really relate to the issue.  But let's suppose it were
implemented using magic-mode-alist.  I think the right thing to
do for these files is treat them as shell scripts.  (That is what
happens now).

If in some case you think it makes sense to edit the file
in HTML mode, you could do M-x html-mode RET.