Add clang-format check to CI (#1683)

This adds clang-format check to the CI. This only checks the diff so it
doesn't affect the other parts of the codebase. Also generated files in
src/prebuilt/ directories are excluded from the check. A new
src/prebuilt/.clang-format is added to disable the check in the
directory.

scripts/clang-format-diff.sh is copied from the same file we are using in
Binaryen.

1 files changed, 24 insertions, 0 deletions

diff --git a/scripts/clang-format-diff.sh b/scripts/clang-format-diff.sh
new file mode 100755
index 00000000..01a813f2
--- /dev/null
+++ b/scripts/clang-format-diff.sh
@@ -0,0 +1,24 @@
+#!/bin/bash
+
+set -o errexit
+set -o pipefail
+
+if [ -n "$1" ]; then
+  BRANCH="$1"
+elif [ -n "$GITHUB_BASE_REF" ]; then
+  BRANCH="origin/$GITHUB_BASE_REF"
+else
+  BRANCH="@{upstream}"
+fi
+
+MERGE_BASE=$(git merge-base $BRANCH HEAD)
+FORMAT_MSG=$(git clang-format $MERGE_BASE -q --diff -- src/)
+if [ -n "$FORMAT_MSG" -a "$FORMAT_MSG" != "no modified files to format" ]
+then
+  echo "Please run git clang-format before committing, or apply this diff:"
+  echo
+  # Run git clang-format again, this time without capruting stdout.  This way
+  # clang-format format the message nicely and add color.
+  git clang-format $MERGE_BASE -q --diff -- src/
+  exit 1
+fi