> by far the most common reason I have seen ImageMagick installed on macOS
Experience varies, but I'm pretty sure IM on macOS is more often used as standalone tools. Most of those 8 million downloads could well be on Linux web servers, and I'm pretty sure PHP bindings for IM are more prevalent than the Ruby binding on servers.
> what exists that only builds against ImageMagick@7?
Homebrew ships cutting edge software. That's the nature of the project.
> Is there some benefit the plethora of updates is providing?
Probably not until you have a CVE.
> I guess this is one of the reasons brew update and the Internet exist.
Well, we're talking about user-hosted taps here... Not really our problem, but still.
Not sure whether dfsg stripping causes problems, I assume not. Two issues:
1. Only a handful of versions are available, most are skipped;
1. Debian removes old tarballs on a regular basis, too.
> Perhaps "someone" should convince upstream to knock that behavior off.
That "someone" might need to foot the bill (which might be negligible; I've no idea).
> My recommendation is that you host this in your own tap for the time being.
The problem with that, in the case of IM, is that it is updated frequently, and whenever an update is issued the old tarball is removed from the server. That's why we brew mirror the tarballs.
But indeed, a formula like this wouldn't work very well. The best compromise is to mark it as keg only, and deal with the hassle of having to specify the opt paths (`PATH`, `LDFLAGS`, `CPPFLAGS`, `PKG_CONFIG_PATH`) where necessary (which isn't always possible in obscure/hand-crafted build systems), or force link it if you don't need any revdeps.
At the very least it comes down to
> I do not think sufficient need for this formula has been demonstrated.
Since we don't really do downgrades here, I guess now we need to figure out a way to include an IMv6 formula (I can keep bumping/maintaining it). Keep in mind that the AT_VERSION syntax was designed for libraries (which should be handled transparently), not for users to type, so `imagemagick@6` is not ideal.