`ruff:ignore` should be processed as a pragma in `contains_pragma_comment`

[A5rocks]

Describe the bug

ruff:ignore is not processed as a pragma.

To Reproduce

For example, take this code:

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx = 5  # ruff:ignore[bweh]

And run it with these arguments:

$ black x.py

The resulting output is:

--- x.py        2026-07-26 00:36:44.849442+00:00
+++ x.py        2026-07-26 00:36:45.724865+00:00
@@ -1 +1,3 @@
-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx = 5  # ruff: ignore[bweh]
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx = (
+    5  # ruff: ignore[bweh]
+)

Expected behavior

No reformatting (which is what happens if you replace this with type: ignore).

Environment

• Black's version: 26.5.1
• OS and Python version: macOS CPython 3.14.2

Additional context

This is probably going to become more popular as ruff has a rule in preview that converts all noqa to ruff:ignore. See https://docs.astral.sh/ruff/rules/noqa-comments/

[JelleZijlstra]

See also #3569 and #3946. I'm a bit wary of privileging comments understood by particular third-party tools.

[jakkdl]

I think the downsides of treating all # xxx: yyy comments as special are likely to be fairly small, and would save a lot of small pain. There are going to be cases where that will no longer fix normal comments that happen to have a colon in them, and distinguishing those cases might be more trouble than it's worth, but I think the net effect is positive.

I personally also like the suggestion of #3569 of having this configurable.

Trying to enumerate common tools would of course work as well, but would be a pain to maintain.

[cobaltt7]

I think the downsides of treating all # xxx: yyy comments as special are likely to be fairly small, and would save a lot of small pain.

https://github.com/search?q=%2F%5B%5E%5Cs%5D+%2B%23+%5Cw%2B%3A+*%5B%5E%5Cn%5D%2F+language%3Apython&type=code

I feel like there's too many non-pragma comments here for that to be a good idea