[llvm] [llvm-lit][test] Precommit tests for lit's built-in cat command (PR #101530)

[James Henderson via llvm-commits]

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@@ -0,0 +1,50 @@
+## C Program to generate all ASCII characters in allchars
+# #include <stdio.h>
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jh7370 wrote:

This code is still part of the comment, so should use `##` for the comment markers. That being said, I don't think it's useful. I think instead, just summarise the contents of `allchars.txt` something like "allchars.txt contains every possible byte value in sequence, and no other characters." This should appear in both test files that use it (so if we drop one, we still have the explanation in the other).

https://github.com/llvm/llvm-project/pull/101530