util/gitconfig/pre-commit: Use clang-format to sanitise commits

Use the `git-format' tool to sanitise coreboot commits such that
they conform to coreboot's coding style.

This fancy piece of machinary allows one to have LibFormat from
Clang to automatically check your commit conforms to coreboot's
coding style, fix any issues automatically and provides you a
diff you may review and apply at your convenience.

N.B. When the `clang-format' binary is not found we issue a warning
that the test was skipped and carry on as usual. Hence, this is
strictly non-enforcing at this current time. You may use it at your
leisure.

Change-Id: If49017ea82f0707efd47cae5978a286a9af8f3b7
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: https://review.coreboot.org/c/8037
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

3 files changed, 151 insertions, 2 deletions

diff --git a/Makefile.inc b/Makefile.inc
index b25ac6b426..2741b19ffa 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -83,7 +83,7 @@ files_added:: build_complete
 
 #######################################################################
 # our phony targets
-PHONY+= clean-abuild coreboot build-dirs build_complete
+PHONY+= clean-abuild coreboot check-style build-dirs build_complete
 
 #######################################################################
 # root source directories of coreboot
@@ -606,6 +606,12 @@ printcrt0s:
 update:
 	dongle.py -c /dev/term/1 $(obj)/coreboot.rom EOF
 
+check-style:
+	grep "^# DESCR:" util/lint/check-style | sed "s,.*DESCR: *,,"
+	echo "========"
+	util/lint/check-style
+	echo "========"
+
 gitconfig:
 	util/gitconfig/gitconfig.sh "$(MAKE)"
 
diff --git a/util/gitconfig/pre-commit b/util/gitconfig/pre-commit
index 0644b7ff86..78b2509eba 100755
--- a/util/gitconfig/pre-commit
+++ b/util/gitconfig/pre-commit
@@ -18,7 +18,7 @@
 set -e # -o errexit
 set -u # -o nounset
 
-%MAKE% lint-stable
+%MAKE% check-style lint-stable
 
 PATCHDIFF=$(git diff --cached --src-prefix=a/ --dst-prefix=b/)
 if printf "%s\n" "$PATCHDIFF" | grep -q "@@"; then
diff --git a/util/lint/check-style b/util/lint/check-style
new file mode 100755
index 0000000000..1ac51b4d1a
--- /dev/null
+++ b/util/lint/check-style
@@ -0,0 +1,143 @@
+#!/bin/bash
+# git pre-commit hook that runs an clang-format stylecheck.
+# Features:
+#  - abort commit when commit does not comply with the style guidelines
+#  - create a patch of the proposed style changes
+#
+# modifications for clang-format by rene.milk@wwu.de
+# This file is part of a set of unofficial pre-commit hooks available
+# at github.
+# Link:    https://github.com/githubbrowser/Pre-commit-hooks
+# Contact: David Martin, david.martin.mailbox@googlemail.com
+
+# DESCR: Checking that VCS 'staged' source conforms to coding style
+
+##################################################################
+# SETTINGS
+# set path to clang-format binary
+CLANG_FORMAT="/usr/bin/clang-format"
+
+# remove any older patches from previous commits. Set to true or false.
+# DELETE_OLD_PATCHES=false
+DELETE_OLD_PATCHES=false
+
+# only parse files with the extensions in FILE_EXTS. Set to true or false.
+# if false every changed file in the commit will be parsed with clang-format.
+# if true only files matching one of the extensions are parsed with clang-format.
+# PARSE_EXTS=true
+PARSE_EXTS=true
+
+# file types to parse. Only effective when PARSE_EXTS is true.
+# FILE_EXTS=".c .h .cpp .hpp"
+FILE_EXTS=".c .h .cpp .hpp .cc .hh .cxx"
+
+##################################################################
+# There should be no need to change anything below this line.
+
+# Reference: http://stackoverflow.com/questions/1055671/how-can-i-get-the-behavior-of-gnus-readlink-f-on-a-mac
+canonicalize_filename () {
+    local target_file=$1
+    local physical_directory=""
+    local result=""
+
+    # Need to restore the working directory after work.
+    pushd `pwd` > /dev/null
+
+    cd "$(dirname "$target_file")"
+    target_file=`basename $target_file`
+
+    # Iterate down a (possible) chain of symlinks
+    while [ -L "$target_file" ]
+    do
+        target_file=$(readlink "$target_file")
+        cd "$(dirname "$target_file")"
+        target_file=$(basename "$target_file")
+    done
+
+    # Compute the canonicalized name by finding the physical path
+    # for the directory we're in and appending the target file.
+    physical_directory=`pwd -P`
+    result="$physical_directory"/"$target_file"
+
+    # restore the working directory after work.
+    popd > /dev/null
+
+    echo "$result"
+}
+
+# exit on error
+set -e
+
+# check whether the given file matches any of the set extensions
+matches_extension() {
+    local filename=$(basename "$1")
+    local extension=".${filename##*.}"
+    local ext
+
+    for ext in $FILE_EXTS; do [[ "$ext" == "$extension" ]] && return 0; done
+
+    return 1
+}
+
+# necessary check for initial commit
+if git rev-parse --verify HEAD >/dev/null 2>&1 ; then
+    against=HEAD
+else
+    # Initial commit: diff against an empty tree object
+    against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+fi
+
+if [ ! -x "$CLANG_FORMAT" ] ; then
+    printf "Warning: clang-format executable not found.\n"
+    printf "Set the correct path in $(canonicalize_filename "$0").\n"
+    printf "Skipping clang-format style check test.\n"
+#    exit 1
+    exit 0
+fi
+
+# create a random filename to store our generated patch
+prefix="pre-commit-clang-format"
+suffix="$(date +%s)"
+patch="/tmp/$prefix-$suffix.patch"
+
+# clean up any older clang-format patches
+$DELETE_OLD_PATCHES && rm -f /tmp/$prefix*.patch
+
+# create one patch containing all changes to the files
+git diff-index --cached --diff-filter=ACMR --name-only $against -- | while read file;
+do
+    # ignore file if we do check for file extensions and the file
+    # does not match any of the extensions specified in $FILE_EXTS
+    if $PARSE_EXTS && ! matches_extension "$file"; then
+        continue;
+    fi
+
+    # clang-format our sourcefile, create a patch with diff and append it to our $patch
+    # The sed call is necessary to transform the patch from
+    #    --- $file timestamp
+    #    +++ - timestamp
+    # to both lines working on the same file and having a a/ and b/ prefix.
+    # Else it can not be applied with 'git apply'.
+    "$CLANG_FORMAT" -style=file "$file" | \
+        diff -u "$file" - | \
+        sed -e "1s|--- |--- a/|" -e "2s|+++ -|+++ b/$file|" >> "$patch"
+done
+
+# if no patch has been generated all is ok, clean up the file stub and exit
+if [ ! -s "$patch" ] ; then
+    printf "Files in this commit comply with the clang-format rules.\n"
+    rm -f "$patch"
+    exit 0
+fi
+
+# a patch has been created, notify the user and exit
+printf "\nThe following differences were found between the code to commit "
+printf "and the clang-format rules:\n\n"
+cat "$patch"
+
+printf "\nYou can apply these changes with:\n git apply $patch\n"
+printf "(may need to be called from the root directory of your repository)\n"
+printf "Aborting commit. Apply changes and commit again or skip checking with"
+printf " --no-verify (not recommended).\n"
+
+exit 1