ci/style-check: add RemoveBracesLLVM in CI job

For 'clang-format', setting 'RemoveBracesLLVM' to 'true', adds a check
to ensure we avoid curly braces for single-statement bodies in
conditional blocks.

However, the option does come with two warnings [1]:

    This option will be renamed and expanded to support other styles.

and

    Setting this option to true could lead to incorrect code formatting
    due to clang-format’s lack of complete semantic information. As
    such, extra care should be taken to review code changes made by
    this option.

The latter seems to be of concern. While we want to experiment with the
rule, adding it to the in-tree '.clang-format' could affect end-users.
Let's only add it to the CI jobs for now. With time, we can evaluate
its efficacy and decide if we want to add it to '.clang-format' or
retract it entirely. We do so, by adding the existing rules in
'.clang-format' and this rule to a temp file outside the working tree,
which is then used by 'git clang-format'. This ensures we don't murk
with files in-tree.

[1]: https://clang.llvm.org/docs/ClangFormatStyleOptions.html#removebracesllvm

Signed-off-by: Karthik Nayak <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: KarthikNayak

ci/run-style-check.sh

@@ -5,4 +5,21 @@
 
 baseCommit=$1
 
-git clang-format --style file --diff --extensions c,h "$baseCommit"
+# Remove optional braces of control statements (if, else, for, and while)
+# according to the LLVM coding style. This avoids braces on simple
+# single-statement bodies of statements but keeps braces if one side of
+# if/else if/.../else cascade has multi-statement body.
+#
+# As this rule comes with a warning [1], we want to experiment with it
+# before adding it in-tree. since the CI job for the style check is allowed
+# to fail, appending the rule here allows us to validate its efficacy.
+# While also ensuring that end-users are not affected directly.
+#
+# [1]: https://clang.llvm.org/docs/ClangFormatStyleOptions.html#removebracesllvm
+{
+	cat .clang-format
+	echo "RemoveBracesLLVM: true"
+} >/tmp/clang-format-rules
+
+git clang-format --style=file:/tmp/clang-format-rules \
+	--diff --extensions c,h "$baseCommit"