Meta: Add a script check the presence of "#pragma once" in header files

.. and make travis run it.

I renamed check-license-headers.sh to check-style.sh and expanded it so
that it now also checks for the presence of "#pragma once" in .h files.

It also checks the presence of a (single) blank line above and below the
"#pragma once" line.

I also added "#pragma once" to all the files that need it: even the ones
we are not check.
I also added/removed blank lines in order to make the script not fail.

I also ran clang-format on the files I modified.

Meta/check-license-headers.sh

@@ -1,30 +0,0 @@
-#!/bin/bash
-
-script_path=$(cd -P -- "$(dirname -- "$0")" && pwd -P)
-cd "$script_path/.." || exit 1
-
-# We simply check if the file starts with:
-# /*
-#  * Copyright
-PATTERN=$'^/\*\n \* Copyright'
-ERRORS=()
-
-while IFS= read -r f; do
-    if [[ ! $(cat "$f") =~ $PATTERN ]]; then
-        ERRORS+=("$f")
-    fi
-done < <(git ls-files -- \
-'*.cpp' \
-'*.h' \
-':!:Tests' \
-':!:Base' \
-':!:Kernel/FileSystem/ext2_fs.h' \
-':!:Libraries/LibC/getopt.cpp' \
-':!:Libraries/LibCore/puff.h' \
-':!:Libraries/LibELF/exec_elf.h' \
-)
-
-if (( ${#ERRORS[@]} )); then
-    echo "Files missing license headers: ${ERRORS[*]}"
-    exit 1
-fi

Meta/check-style.sh

@@ -0,0 +1,56 @@
+#!/bin/bash
+
+script_path=$(cd -P -- "$(dirname -- "$0")" && pwd -P)
+cd "$script_path/.." || exit 1
+
+# We simply check if the file starts with:
+# /*
+#  * Copyright
+LICENSE_HEADER_PATTERN=$'^/\*\n \* Copyright'
+MISSING_LICENSE_HEADER_ERRORS=()
+
+# We check that "#pragma once" is present
+PRAGMA_ONCE_PATTERN='#pragma once'
+MISSING_PRAGMA_ONCE_ERRORS=()
+
+# We make sure that there's a blank line before and after pragma once
+GOOD_PRAGMA_ONCE_PATTERN=$'(^|\\S\n\n)#pragma once(\n\n\\S.|$)'
+BAD_PRAGMA_ONCE_ERRORS=()
+
+while IFS= read -r f; do
+    file_content="$(< "$f")"
+    if [[ ! "$file_content" =~ $LICENSE_HEADER_PATTERN ]]; then
+        MISSING_LICENSE_HEADER_ERRORS+=("$f")
+    fi
+    if [[ "$f" =~ \.h$ ]]; then
+        if [[ ! "$file_content" =~ $PRAGMA_ONCE_PATTERN ]]; then
+            MISSING_PRAGMA_ONCE_ERRORS+=("$f")
+        elif [[ ! "$file_content" =~ $GOOD_PRAGMA_ONCE_PATTERN ]]; then
+            BAD_PRAGMA_ONCE_ERRORS+=("$f")
+        fi
+    fi
+done < <(git ls-files -- \
+    '*.cpp' \
+    '*.h' \
+    ':!:Tests' \
+    ':!:Base' \
+    ':!:Kernel/FileSystem/ext2_fs.h' \
+    ':!:Libraries/LibC/getopt.cpp' \
+    ':!:Libraries/LibCore/puff.h' \
+    ':!:Libraries/LibELF/exec_elf.h' \
+)
+
+exit_status=0
+if (( ${#MISSING_LICENSE_HEADER_ERRORS[@]} )); then
+    echo "Files missing license headers: ${MISSING_LICENSE_HEADER_ERRORS[*]}"
+    exit_status=1
+fi
+if (( ${#MISSING_PRAGMA_ONCE_ERRORS[@]} )); then
+    echo "Header files missing \"#pragma once\": ${MISSING_PRAGMA_ONCE_ERRORS[*]}"
+    exit_status=1
+fi
+if (( ${#BAD_PRAGMA_ONCE_ERRORS[@]} )); then
+    echo "\"#pragma once\" should have a blank line before and after in these files: ${BAD_PRAGMA_ONCE_ERRORS[*]}"
+    exit_status=1
+fi
+exit "$exit_status"