tools/checkpatch.sh: check format for all commits in patch

If more than one commit is present in the patch, the commit format
must be checked separately for each commit in patch, otherwise not
all errors are detected.

Signed-off-by: raiden00pl <raiden00@railab.me>

tools/checkpatch.sh

@@ -334,15 +334,23 @@ check_msg() {
   fi
 
   if (( $num_lines < $min_num_lines && $signedoffby_found == 1 )); then
-      echo "Missing git commit message."
-      fail=1
+    echo "Missing git commit message"
+    fail=1
   fi
 }
 
 check_commit() {
   if [ $message != 0 ]; then
-    msg=`git show -s --format=%B $1`
-    check_msg <<< "$msg"
+    # check each commit format separately if this is a series of commits
+    if [[ $1 =~  HEAD ]]; then
+      for commit in $(git rev-list --no-merges $1); do
+        msg=`git show -s --format=%B $commit`
+        check_msg <<< "$msg"
+      done
+    else
+      msg=`git show -s --format=%B $1`
+      check_msg <<< "$msg"
+    fi
   fi
   diffs=`git diff $1`
   check_ranges <<< "$diffs"