feat(util): parallelize srcinfo generation

Heavily improve the runtime of huge split packages, by creating an own
parallelized high level implementation of the makepkg low level building
blocks for srcinfo generation.

This reduces the runtine to generate the srcinfo file for thunderbird
from 24 seconds down to 1 second.

2 files changed, 72 insertions, 2 deletions

diff --git a/src/lib/build/build.sh b/src/lib/build/build.sh
index e0982e4..8b4240c 100644
--- a/src/lib/build/build.sh
+++ b/src/lib/build/build.sh
@@ -14,6 +14,8 @@ source "${_DEVTOOLS_LIBRARY_DIR}"/lib/db/update.sh
 source "${_DEVTOOLS_LIBRARY_DIR}"/lib/release.sh
 # shellcheck source=src/lib/util/git.sh
 source "${_DEVTOOLS_LIBRARY_DIR}"/lib/util/git.sh
+# shellcheck source=src/lib/util/srcinfo.sh
+source "${_DEVTOOLS_LIBRARY_DIR}"/lib/util/srcinfo.sh
 # shellcheck source=src/lib/util/pacman.sh
 source "${_DEVTOOLS_LIBRARY_DIR}"/lib/util/pacman.sh
 # shellcheck source=src/lib/valid-repos.sh
@@ -26,8 +28,7 @@ source "${_DEVTOOLS_LIBRARY_DIR}"/lib/valid-inspect.sh
 source /usr/share/makepkg/util/config.sh
 source /usr/share/makepkg/util/message.sh
 
-set -e
-set -o pipefail
+set -eo pipefail
 
 
 pkgctl_build_usage() {
diff --git a/src/lib/util/srcinfo.sh b/src/lib/util/srcinfo.sh
new file mode 100644
index 0000000..b646dc3
--- /dev/null
+++ b/src/lib/util/srcinfo.sh
@@ -0,0 +1,69 @@
+#!/hint/bash
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+[[ -z ${DEVTOOLS_INCLUDE_UTIL_SRCINFO_SH:-} ]] || return 0
+DEVTOOLS_INCLUDE_UTIL_SRCINFO_SH=1
+
+_DEVTOOLS_LIBRARY_DIR=${_DEVTOOLS_LIBRARY_DIR:-@pkgdatadir@}
+# shellcheck source=src/lib/common.sh
+source "${_DEVTOOLS_LIBRARY_DIR}"/lib/common.sh
+
+source /usr/share/makepkg/util/util.sh
+source /usr/share/makepkg/srcinfo.sh
+
+set -eo pipefail
+
+
+print_srcinfo() {
+	local pkgpath=${1:-.}
+	local outdir pkg pid
+	local pids=()
+
+	# source the PKGBUILD
+	# shellcheck source=contrib/makepkg/PKGBUILD.proto
+	. "${pkgpath}"/PKGBUILD
+
+	# run without parallelization for single packages
+	if (( ${#pkgname[@]} == 1 )); then
+		write_srcinfo_content
+		return 0
+	fi
+
+	[[ -z ${WORKDIR:-} ]] && setup_workdir
+	outdir=$(mktemp --directory --tmpdir="${WORKDIR}" pkgctl-srcinfo.XXXXXXXXXX)
+
+	# fork workload for each split pkgname
+	for pkg in "${pkgname[@]}"; do
+		(
+			# deactivate errexit to avoid makepkg abort on grep_function
+			set +e
+			srcinfo_write_package "$pkg" > "${outdir}/${pkg}"
+		)&
+		pids+=($!)
+	done
+
+	# join workload
+	for pid in "${pids[@]}"; do
+		if ! wait "${pid}"; then
+			return 1
+		fi
+	done
+
+	# collect output
+	srcinfo_write_global
+	for pkg in "${pkgname[@]}"; do
+		srcinfo_separate_section
+		cat "${outdir}/${pkg}"
+	done
+}
+
+write_srcinfo_file() {
+	local pkgpath=${1:-.}
+	stat_busy 'Generating .SRCINFO'
+	if ! print_srcinfo "${pkgpath}" > "${pkgpath}"/.SRCINFO; then
+		error 'Failed to write .SRCINFO file'
+		return 1
+	fi
+	stat_done
+}