[llvm] [llvm-lit][test] Precommit tests for curly braces in lit internal shell (PR #102976)

[Paul Kirth via llvm-commits]

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+## Test curly braces used in grouping commands.
+
+## Test one command inside curly brace.
+# RUN: { echo bar; } | FileCheck --check-prefix=ONE-CMD %s
+
+# ONE-CMD: bar
+
+## Test two commands inside curly brace.
+# RUN: { echo foo; echo bar; } | FileCheck --check-prefix=TWO-CMDS %s
+
+# TWO-CMDS: foo
+# TWO-CMDS: bar
+
+## Test nested curly brace.
+# RUN: { echo foo; { echo bar; echo baz; }; } | FileCheck --check-prefix=NESTED %s
+# RUN: { { echo foo; echo bar; }; echo baz; } | FileCheck --check-prefix=NESTED %s
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ilovepi wrote:

I'm not sure this is checking things well enough. The nested `{...}` probably needs to result in something that's distinct from the regular case. As written, you cant distinguish the nested version from the un-nested version. Maybe you can use a `|` or file redirection + `cat`?

https://github.com/llvm/llvm-project/pull/102976