[libcamera-devel] [PATCH v3] build: Preserve upstream git versioning using meson dist

[Naushir Patuck]

When distributions build and package libcamera libraries, they may not
necessarily run the build in the upstream source tree. In these cases, the git
SHA1 versioning information will be lost.

This change addresses that problem by requiring package managers to run
'meson dist' to create a tarball of the source files and build from there.
On runing 'meson dist', the utils/run-dist.sh script will create a
.tarball-version file in the release tarball with the version string generated
from the existing utils/gen-version.sh script.

The utils/gen-version.sh script has been updated to check for the presence of
this .tarball-version file and read the version string from it instead of
creating one.

Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
---
 meson.build               |  3 +++
 src/libcamera/meson.build | 11 +++++------
 utils/gen-version.sh      |  9 +++++++++
 utils/run-dist.sh         | 11 +++++++++++
 4 files changed, 28 insertions(+), 6 deletions(-)
 create mode 100644 utils/run-dist.sh

diff --git a/meson.build b/meson.build
index a49c484fe64e..67be6762108c 100644
--- a/meson.build
+++ b/meson.build
@@ -24,6 +24,9 @@ endif
 
 libcamera_version = libcamera_git_version.split('+')[0]
 
+# This script gererates the .tarball-version file on a 'meson dist' command.
+meson.add_dist_script('utils/run-dist.sh')
+
 # Configure the build environment.
 cc = meson.get_compiler('c')
 cxx = meson.get_compiler('cpp')
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 243dd3c180eb..360eaf80ecf1 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -93,12 +93,11 @@ endforeach
 
 libcamera_sources += control_sources
 
-gen_version = meson.source_root() / 'utils' / 'gen-version.sh'
-
-version_cpp = vcs_tag(command : [gen_version, meson.build_root()],
-                      input : 'version.cpp.in',
-                      output : 'version.cpp',
-                      fallback : meson.project_version())
+version_data = configuration_data()
+version_data.set('VCS_TAG', libcamera_git_version)
+version_cpp = configure_file(input : 'version.cpp.in',
+                             output : 'version.cpp',
+                             configuration : version_data)
 
 libcamera_sources += version_cpp
 
diff --git a/utils/gen-version.sh b/utils/gen-version.sh
index b09ad495f86a..216b1ff0b33e 100755
--- a/utils/gen-version.sh
+++ b/utils/gen-version.sh
@@ -5,6 +5,15 @@
 
 build_dir="$1"
 
+# If .tarball-version exists, output the version string from the file and exit.
+# This file is auto-generated on a 'meson dist' command from the run-dist.sh
+# script.
+if [ -f "${MESON_SOURCE_ROOT}"/.tarball-version ]
+then
+	cat "${MESON_SOURCE_ROOT}"/.tarball-version
+	exit 0
+fi
+
 # Bail out if the directory isn't under git control
 src_dir=$(git rev-parse --git-dir 2>&1) || exit 1
 src_dir=$(readlink -f "$src_dir/..")
diff --git a/utils/run-dist.sh b/utils/run-dist.sh
new file mode 100644
index 000000000000..e89c3733b56c
--- /dev/null
+++ b/utils/run-dist.sh
@@ -0,0 +1,11 @@
+#!/bin/sh
+
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# On a meson dist run, generate the version string and store it in a file.
+# This will later be picked up by the utils/gen-version.sh script and used
+# instead of re-generating it. This way, if we are not building in the upstream
+# git source tree, the upstream version information will be preserved.
+
+cd "$MESON_SOURCE_ROOT" || return
+./utils/gen-version.sh > "$MESON_DIST_ROOT"/.tarball-version
-- 
2.25.1