clang-format: Add pre-commit hook

Derived from https://github.com/githubbrowser/Pre-commit-hooks
and https://gitlab.cern.ch/GeantV/geant/blob/master/hooks/pre-commit-clang-format

(cherry picked from commit 0e4ee5935a)

misc/hooks/README.md

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+# Git hooks for Godot Engine
+
+This folder contains git hooks meant to be installed locally by Godot Engine
+contributors to make sure they comply with our requirements.
+
+## List of hooks
+
+- Pre-commit hook for clang-format: Applies clang-format to the staged files
+  before accepting a commit; blocks the commit and generates a patch if the
+  style is not respected.
+  Should work on Linux and macOS. You may need to edit the file if your
+  clang-format binary is not in the $PATH, or if you want to enable colored
+  output with pygmentize.
+
+## Installation
+
+Copy all the files from this folder into your .git/hooks folder, and make sure
+the hooks and helper scripts are executable.

misc/hooks/canonicalize_filename.sh

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+#!/bin/sh
+
+# Provide the canonicalize filename (physical filename with out any symlinks)
+# like the GNU version readlink with the -f option regardless of the version of
+# readlink (GNU or BSD).
+
+# 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
+
+###########################################################
+# There should be no need to change anything below this line.
+
+# Canonicalize by recursively following every symlink in every component of the
+# specified filename.  This should reproduce the results of the GNU version of
+# readlink with the -f option.
+#
+# Reference: http://stackoverflow.com/questions/1055671/how-can-i-get-the-behavior-of-gnus-readlink-f-on-a-mac
+canonicalize_filename () {
+    local target_file="$1"
+    local physical_directory=""
+    local result=""
+
+    # Need to restore the working directory after work.
+    local working_dir="`pwd`"
+
+    cd -- "$(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.
+    cd -- "$working_dir"
+
+    echo "$result"
+}

misc/hooks/pre-commit

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+#!/bin/sh
+# Git pre-commit hook that runs multiple hooks specified in $HOOKS.
+# Make sure this script is executable. Bypass hooks with git commit --no-verify.
+
+# This file is part of a set of unofficial pre-commit hooks available
+# at github.
+# Link:    https://github.com/githubbrowser/Pre-commit-hooks
+# Contact: David Martin, david.martin.mailbox@googlemail.com
+
+
+###########################################################
+# CONFIGURATION:
+# pre-commit hooks to be executed. They should be in the same .git/hooks/ folder
+# as this script. Hooks should return 0 if successful and nonzero to cancel the
+# commit. They are executed in the order in which they are listed.
+#HOOKS="pre-commit-compile pre-commit-uncrustify"
+HOOKS="pre-commit-clang-format"
+###########################################################
+# There should be no need to change anything below this line.
+
+. "$(dirname -- "$0")/canonicalize_filename.sh"
+
+# exit on error
+set -e
+
+# Absolute path to this script, e.g. /home/user/bin/foo.sh
+SCRIPT="$(canonicalize_filename "$0")"
+
+# Absolute path this script is in, thus /home/user/bin
+SCRIPTPATH="$(dirname -- "$SCRIPT")"
+
+
+for hook in $HOOKS
+do
+    echo "Running hook: $hook"
+    # run hook if it exists
+    # if it returns with nonzero exit with 1 and thus abort the commit
+    if [ -f "$SCRIPTPATH/$hook" ]; then
+        "$SCRIPTPATH/$hook"
+        if [ $? != 0 ]; then
+            exit 1
+        fi
+    else
+        echo "Error: file $hook not found."
+        echo "Aborting commit. Make sure the hook is in $SCRIPTPATH and executable."
+        echo "You can disable it by removing it from the list in $SCRIPT."
+        echo "You can skip all pre-commit hooks with --no-verify (not recommended)."
+        exit 1
+    fi
+done

misc/hooks/pre-commit-clang-format

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+#!/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
+
+# Some quality of life modifications made for Godot Engine.
+
+##################################################################
+# SETTINGS
+# Set path to clang-format binary
+# CLANG_FORMAT="/usr/bin/clang-format"
+CLANG_FORMAT=`which 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 .m"
+
+# Use pygmentize instead of cat to parse diff with highlighting.
+# Install it with `pip install pygments` (Linux) or `easy_install Pygments` (Mac)
+# READER="pygmentize -l diff"
+READER=cat
+
+##################################################################
+# There should be no need to change anything below this line.
+
+. "$(dirname -- "$0")/canonicalize_filename.sh"
+
+# exit on error
+set -e
+
+# check whether the given file matches any of the set extensions
+matches_extension() {
+    local filename=$(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 "Error: clang-format executable not found.\n"
+    printf "Set the correct path in $(canonicalize_filename "$0").\n"
+    exit 1
+fi
+
+# create a random filename to store our generated patch
+prefix="pre-commit-clang-format"
+suffix="$(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"
+$READER "$patch"
+printf "\n"
+
+# Allows us to read user input below, assigns stdin to keyboard
+exec < /dev/tty
+
+while true; do
+    read -p "Do you want to apply that patch (Y - Apply, N - Do not apply, S - Apply and stage files)? [Y/N/S] " yn
+    case $yn in
+        [Yy] ) git apply $patch;
+        printf "The patch was applied. You can now stage the changes and commit again.\n\n";
+        break
+        ;;
+        [Nn] ) 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\n";
+        break
+        ;;
+        [Ss] ) git apply $patch;
+        git diff-index --cached --diff-filter=ACMR --name-only $against -- | while read file;
+        do git add $file;
+        done
+        printf "The patch was applied and the changed files staged. You can now commit.\n\n";
+        break
+        ;;
+        * ) echo "Please answer yes or no."
+        ;;
+    esac
+done
+exit 1 # we don't commit in any case