Formatting: exclude generated files from git formatting hook

Add a .gitattributes files to provide a place to store file
attributes. Add a custom attribute for files that should be under
KiCad style guidelines.

Exclude generated files from the style enforcement. So far:

* bitmap .cpp files
* wxFormBuilder base classes
* Lemon grammars

It's now trivial to add the 'generated' attribute to any such
file.

Putting this into .gitattributes also means it can be retreived
programmatically, by other scripts, git alaises or on the command
line.

Use the attributes to provide a utility script to show or apply
formatting to controlled files (plain git clang-format won't
pick up our custom git attributes). Add details for the script in
the dev docs.

Also modiify the check-format hook to follow the .gitattributes
and only apply to cached (staged for commit) changes. Then you
won't be stopped committing because of bad formatting in unstaged
changed, or uncontrolled files.

Concept and some aspects of the implementation inspired by
CMake commit d5f39a56 [1].

[1]: d5f39a56a4

tool

.gitattributes

@@ -0,0 +1,31 @@
+
+# Custom attribute to mark source files using KiCad C++ formatting
+[attr]kicad-cpp-source whitepace=tab-in-indent format.clang-format-kicad
+
+# Custom attribute to mark KiCad's own CMake files
+[attr]kicad-cmake-source whitespace=tab-in-indent
+
+# Custom attribute for auto-generated sources:
+# * Do not perform whitespace checking
+# * Do not format
+[attr]generated whitespace=-tab-in-indent,-indent-with-non-tab -format.clang-format-kicad
+
+# By default, all C and C++ files conform to KiCad formatting,
+# unless overridden
+*.c         kicad-cpp-source
+*.cpp       kicad-cpp-source
+*.h         kicad-cpp-source
+
+*.cmake     kicad-cmake-source
+*.txt       kicad-cmake-source
+
+# Compiled bitmap sources
+bitmaps_png/cpp_*/*.cpp     generated
+
+# wxFormBuilder-generated files
+**/dialog*/*_base.cpp       generated
+**/dialog*/*_base.h         generated
+
+# Lemon grammars
+common/libeval/grammar.c    generated
+common/libeval/grammar.h    generated

.githooks/pre-commit.d/50-check-format

@@ -30,20 +30,48 @@ check_git_config() {
     fi
 }
 
+get_filtered_filenames()
+{
+    format_attr='clang-format-kicad'
+
+    # command to get list of candidate files
+    git_list_files='git diff --cached --name-only --diff-filter=ACM'
+
+    files=$(${git_list_files} |
+
+        # Filter for format-controlled files
+        git check-attr --stdin format.${format_attr} |
+
+        # output only the file names
+        grep ": set$" |
+        cut -d: -f1)
+
+    echo ${files}
+}
+
 check_clang_format
 check_git_config
 
-readonly out=$(git clang-format -v --diff)
+files_to_check=$(get_filtered_filenames)
+
+if [ -z "${files_to_check}" ]; then
+    # No controlled files to check
+    exit 0;
+fi
+
+git_clang_format_cmd="git clang-format -v --diff -- ${files_to_check}"
+
+readonly out=$(${git_clang_format_cmd})
 
 # In these cases, there is no formatting issues, so we succeed
 if [[ "$out" == *"no modified files to format"* ]]; then exit 0; fi
 if [[ "$out" == *"clang-format did not modify any files"* ]]; then exit 0; fi
 
 # Any other case implies formatting results
-echo "ERROR: you need to run git clang-format on your commit"
+echo "ERROR: you need to run clang-format (e.g. using tools/check_coding.sh) on your commit"
 
 # print the errors to show what's the issue
-git clang-format -v --diff
+${git_clang_format_cmd}
 
 # fail the pre-commit
 exit 1

Documentation/development/coding-style-policy.md

@@ -72,18 +72,25 @@ Set the `git clang-format` tool to use the provided `_clang-format` file:
 
 Then, to enable the format checker, set the `KICAD_CHECK_FORMAT` environment
 variable in your shell. Without this variable, the format checker will not
-run on commit, but you can still use `git clang-format --diff` to check manually.
+run on commit, but you can still check files staged for commit manually:
 
-If enabled, when you commit a change, you will be told if you have caused any
+    tools/check_coding.sh --diff
-style violations (only in your changed code). You can fix them automatically
-with:
 
-    git clang-format
+If the hook is enabled, when you commit a change, you will be told if you
+have caused any style violations (only in your changed code). You can fix your
+staged changes automatically with this tool:
+
+    tools/check_coding.sh
 
 Or you can proceed anyway, if you are sure your style is correct:
 
     git commit --no-verify
 
+The `check_coding.sh` tool has other modes:
+
+* Make (or see only) changes to files modified in the previous commit:
+    * `check_coding.sh --amend [--diff]`
+
 
 # 2. Naming Conventions # {#naming_conventions}
 Before delving into anything as esoteric as indentation and formatting,

tools/check_coding.sh

@@ -0,0 +1,107 @@
+#!/usr/bin/env bash
+
+#  This program source code file is part of KICAD, a free EDA CAD application.
+#
+#  Copyright (C) 2019 Kicad Developers, see AUTHORS.txt for contributors.
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, you may find one here:
+#  http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+#  or you may search the http://www.gnu.org website for the version 2 license,
+#  or you may write to the Free Software Foundation, Inc.,
+#  51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+
+# Simple program to check and fix formatting in KiCad source files,
+# while ignoring violations in "uncontrolled" files, such as generated files
+# or 3rd party sources.
+
+usage='usage: check_coding.sh [<options>] [--]
+     --help                     Print usage plus more detailed help.
+
+     --diff                     Only show proposed changes, do not format files
+
+     --cached                   Re-format changes currently staged for commit
+     --amend                    Re-format changes made in the previous commit
+'
+
+help="$usage"'
+Example to format cached files:
+    check_coding.sh
+
+To show what would be done:
+    check_coding.sh --diff
+'
+
+die() {
+    echo "$@" 1>&2; exit 1
+}
+
+# Parse command-line arguments.
+diff=false
+mode='cached'
+
+while test "$#" != 0; do
+    case "$1" in
+    --diff) diff=true ;;
+    --amend) mode='amend' ;;
+    --cached) mode='cached' ;;
+    --) shift ; break ;;
+    -*) die "$usage" ;;
+    *) break ;;
+    esac
+    shift
+done
+
+test "$#" = 0 || die "$usage"
+
+# This is the main KiCad formatting attribute
+# used by .gitattributes to mark KiCad source files
+format_attribute="format.clang-format-kicad"
+
+format_commit='HEAD'
+
+# Select the git file list command and the commit to check
+case "${mode}" in
+    '')       echo "$usage"; exit 0 ;;
+    amend)
+        # Files changed by the last commit
+        git_list_files='git diff-tree  --diff-filter=ACM --name-only HEAD -r --no-commit-id'
+        format_commit='HEAD^'
+        ;;
+    cached)
+        # Currently staged files
+        git_list_files='git diff-index --diff-filter=ACM --name-only HEAD --cached'
+        ;;
+    *) die "Invalid mode: $mode" ;;
+esac
+
+
+if [ "${diff}" = true ]; then
+    # Only show the proposed changes
+    format_command="git clang-format --diff ${format_commit}"
+else
+    # Actually make the changes
+    format_command="git clang-format ${format_commit}"
+fi
+
+${git_list_files} |
+
+    # Filter sources with the formatting attribute set
+    git check-attr ${format_attribute} --stdin |
+
+    # output only the file names
+    grep ": set$" |
+    cut -d: -f1 |
+
+    # Apply the formatting command
+    xargs -d '\n' ${format_command}