Speed up the Tap#formula_files method

[apainintheneck]

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We already know that files are going to be formula files if they are ruby files since we pull them out of the formula directory so that's all we really need to check for here. I was surprised that Pathname#extname was noticeably slower than turning it into a string and checking the end of it.

$ hyperfine --parameter-list branch master,speed-up-loading-cask-and-formula-file-names --warmup 5 --setup 'git switch {branch}' 'brew cat gimp'
Benchmark 1: brew cat gimp (branch = master)
  Time (mean ± σ):      2.195 s ±  0.031 s    [User: 1.395 s, System: 0.748 s]
  Range (min … max):    2.163 s …  2.273 s    10 runs

Benchmark 2: brew cat gimp (branch = speed-up-loading-cask-and-formula-file-names)
  Time (mean ± σ):      1.845 s ±  0.034 s    [User: 1.073 s, System: 0.718 s]
  Range (min … max):    1.814 s …  1.920 s    10 runs

Summary
  brew cat gimp (branch = speed-up-loading-cask-and-formula-file-names) ran
    1.19 ± 0.03 times faster than brew cat gimp (branch = master)

This also makes it a bit simpler for me to resurrect #15489 since it means there is now one less reference to the Tap#formula_file? method.

[Bo98]

I was surprised that Pathname#extname was noticeably slower than turning it into a string and checking the end of it.

Pathname is pretty bad a lot of the time but in this particular case it may be from

brew/Library/Homebrew/extend/pathname.rb

Lines 238 to 245 in 17e3bee

	bottle_ext, = HOMEBREW_BOTTLES_EXTNAME_REGEX.match(basename).to_a
	return bottle_ext if bottle_ext
	archive_ext = basename[/(\.(tar|cpio|pax)\.(gz|bz2|lz|xz|zst|Z))\Z/, 1]
	return archive_ext if archive_ext
	# Don't treat version numbers as extname.
	return "" if basename.match?(/\b\d+\.\d+[^.]*\Z/) && !basename.end_with?(".7z")

You can test by comparing it to File.extname.

.to_s.ends_with? is technically incorrect if you had a dotfile named .rb, though maybe we don't care too much about that.

[apainintheneck]

Good points all around. I'd forgotten that it'd potentially match a dotfile here when using String#ends_with? and I didn't know that we had a monkey-patched version of Pathname#extname. Switching to using File.extname provides a similar speed up though so this should be fine now.

$ hyperfine --parameter-list branch master,speed-up-loading-cask-and-formula-file-names --warmup 5 --setup 'git switch {branch}' 'brew cat gimp'
Benchmark 1: brew cat gimp (branch = master)
  Time (mean ± σ):      2.109 s ±  0.010 s    [User: 1.349 s, System: 0.726 s]
  Range (min … max):    2.097 s …  2.128 s    10 runs

Benchmark 2: brew cat gimp (branch = speed-up-loading-cask-and-formula-file-names)
  Time (mean ± σ):      1.795 s ±  0.011 s    [User: 1.061 s, System: 0.702 s]
  Range (min … max):    1.777 s …  1.813 s    10 runs

Summary
  brew cat gimp (branch = speed-up-loading-cask-and-formula-file-names) ran
    1.17 ± 0.01 times faster than brew cat gimp (branch = master)

[apainintheneck]

Converting to draft because I think I found an even better approach.

[apainintheneck]

Closing in favor of #18165