Add cmake function to configure git pre-commit hooks

This will allow us to force QS checks before
the developer commits a change. Currently only
clang-format is supported, but as on #plasma and
https://phabricator.kde.org/T11214 discussed we
might want to add different formatters.

By making the checks configurable we are flexible
and can easily extend it.

3 files changed, 82 insertions, 0 deletions

diff --git a/kde-modules/KDEGitCommitHooks.cmake b/kde-modules/KDEGitCommitHooks.cmake
new file mode 100644
index 00000000..90f53844
--- /dev/null
+++ b/kde-modules/KDEGitCommitHooks.cmake
@@ -0,0 +1,66 @@
+#.rst:
+# KDEGitCommitHooks
+# --------------------
+#
+# This module provides a functionality to enforce formatting
+# or in the future other QS checks.
+#
+# This module provides the following function:
+#
+# ::
+#
+#   kde_configure_pre_commit_hook(GIR_DIR <dir> CHECKS <checks...>)
+#
+# This function will create a pre-commit hook which contains all the given checks.
+# In case the source dir does not contain the .git folder, the GIT_DIR
+# parameter can be passed in.
+#
+# Example usage:
+#
+# .. code-block:: cmake
+#
+#   include(KDEGitCommitHooks)
+#   kde_configure_git_pre_commit_hook(CHECKS CLANG_FORMAT)
+#
+# Since 5.79
+
+#=============================================================================
+# SPDX-FileCopyrightText: 2020 Alexander Lohnau <alexander.lohnau@gmx.de>
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+# try to find clang-format in path
+find_program(KDE_CLANG_FORMAT_EXECUTABLE clang-format)
+include(CMakeParseArguments)
+set(PRE_COMMIT_HOOK_UNIX "${CMAKE_CURRENT_LIST_DIR}/kde-git-commit-hooks/pre-commit.in")
+set(CLANG_FORMAT_UNIX "${CMAKE_CURRENT_LIST_DIR}/kde-git-commit-hooks/clang-format.sh")
+
+function(KDE_CONFIGURE_GIT_PRE_COMMIT_HOOK)
+    set(_oneValueArgs GIT_DIR)
+    set(_multiValueArgs CHECKS)
+    cmake_parse_arguments(ARG "" "${_oneValueArgs}" "${_multiValueArgs}" ${ARGN} )
+
+    if(NOT ARG_CHECKS)
+        message(FATAL_ERROR "No checks were specified")
+    endif()
+    if(NOT ARG_GIT_DIR)
+        set(ARG_GIT_DIR "${CMAKE_SOURCE_DIR}/.git")
+    endif()
+
+    # In case of tarballs there is no .git directory
+    if (EXISTS ${ARG_GIT_DIR})
+        # The pre-commit hook is a bash script, consequently it won't work on non-unix platforms
+        if (UNIX)
+            if(KDE_CLANG_FORMAT_EXECUTABLE)
+                list(FIND ARG_CHECKS "CLANG_FORMAT" _index)
+                if (${_index} GREATER -1)
+                    set(CLANG_FORMAT_SCRIPT ${CLANG_FORMAT_UNIX})
+                endif()
+            else()
+                message(WARNING "No clang-format executable was found, skipping the formatting pre-commit hook")
+            endif()
+
+            configure_file(${PRE_COMMIT_HOOK_UNIX} "${ARG_GIT_DIR}/hooks/pre-commit")
+        endif()
+    endif()
+endfunction()
diff --git a/kde-modules/kde-git-commit-hooks/clang-format.sh b/kde-modules/kde-git-commit-hooks/clang-format.sh
new file mode 100755
index 00000000..d351e3cd
--- /dev/null
+++ b/kde-modules/kde-git-commit-hooks/clang-format.sh
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+# Based on okular/hooks/pre-commit, credits go to Albert Astals Cid
+
+readonly output=$(git clang-format -v --diff)
+
+if [[ "$output" == *"no modified files to format"* ]]; then exit 0; fi
+if [[ "$output" == *"clang-format did not modify any files"* ]]; then exit 0; fi
+
+echo "ERROR: You have unformatted changes, please format your files. You can do this using the following commands:"
+echo "       git clang-format --force # format the changed parts"
+echo "       git clang-format --diff # preview the changes done by the formatter"
+exit 1
diff --git a/kde-modules/kde-git-commit-hooks/pre-commit.in b/kde-modules/kde-git-commit-hooks/pre-commit.in
new file mode 100644
index 00000000..36cdfd5d
--- /dev/null
+++ b/kde-modules/kde-git-commit-hooks/pre-commit.in
@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+
+${CLANG_FORMAT_SCRIPT}