libcamera: Auto generate version information

Generate a version string, and provide a global string object which
allows applications to interrogate the current libcamera version
information.

The version header is automatically updated by meson on each build.
The string roughly follows the semver [0] conventions of
major.minor.patch-label as a value.

[0] https://semver.org/

A script (utils/gen-version.sh) is provided which is modelled upon the
processing from autoconf's git-version-gen. The gen-version.sh script
will look for tags in the form vX.Y as starting points for the version
string. While the repository does not have any matching tags, v0.0 will
be assumed, resulting in versions with both major and minor being set to
'0', and the patch count resulting from the number of patches in the
history to that point.

Finally, a uniquely identifying shortened hash is provided from git:

	v0.0.509+0ec0edf7

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

8 files changed, 85 insertions, 13 deletions

diff --git a/Documentation/conf.py b/Documentation/conf.py
index 970edf3d..bffd1d8f 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -23,11 +23,8 @@ project = 'libcamera'
 copyright = '2018-2019, The libcamera documentation authors'
 author = u'Kieran Bingham, Jacopo Mondi, Laurent Pinchart, Niklas Söderlund'
 
-# The short X.Y version
-version = ''
-# The full version, including alpha/beta/rc tags
-release = '0.1'
-
+# Version information is provided by the build environment, through the
+# sphinx command line.
 
 # -- General configuration ---------------------------------------------------
 
diff --git a/Documentation/meson.build b/Documentation/meson.build
index 629e8531..2db80b39 100644
--- a/Documentation/meson.build
+++ b/Documentation/meson.build
@@ -1,4 +1,4 @@
-doc_install_dir = join_paths(get_option('datadir'), 'doc', 'libcamera-@0@'.format(api_version))
+doc_install_dir = join_paths(get_option('datadir'), 'doc', 'libcamera-@0@'.format(meson.project_version()))
 
 #
 # Doxygen
@@ -47,8 +47,11 @@ if sphinx.found()
         'index.rst',
     ]
 
+    release = 'release=' + meson.project_version()
+
     custom_target('documentation',
-                  command : [sphinx, '-q', '-W', '-b', 'html', meson.current_source_dir(), '@OUTPUT@'],
+                  command : [sphinx, '-D', release, '-q', '-W', '-b', 'html',
+                             meson.current_source_dir(), '@OUTPUT@'],
                   input : docs_sources,
                   output : 'html',
                   build_by_default : true,
diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
index 3067120a..6f81f111 100644
--- a/include/libcamera/meson.build
+++ b/include/libcamera/meson.build
@@ -16,6 +16,13 @@ libcamera_api = files([
     'timer.h',
 ])
 
+gen_version = join_paths(meson.source_root(), 'utils', 'gen-version.sh')
+
+version_h = vcs_tag(command : [gen_version, meson.current_source_dir()],
+                    input : 'version.h.in',
+                    output : 'version.h',
+                    fallback : 'v0.0')
+
 gen_header = files('gen-header.sh')
 
 libcamera_h = custom_target('gen-header',
diff --git a/include/libcamera/version.h.in b/include/libcamera/version.h.in
new file mode 100644
index 00000000..e49b3696
--- /dev/null
+++ b/include/libcamera/version.h.in
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * version.h - Library version information
+ *
+ * This file is auto-generated. Do not edit.
+ */
+#ifndef __LIBCAMERA_VERSION_H__
+#define __LIBCAMERA_VERSION_H__
+
+#include <string>
+
+#define LIBCAMERA_VERSION "@VCS_TAG@"
+
+namespace libcamera {
+
+extern const std::string version;
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_VERSION_H__ */
diff --git a/meson.build b/meson.build
index a3b0bc82..342b3cc7 100644
--- a/meson.build
+++ b/meson.build
@@ -1,6 +1,8 @@
 project('libcamera', 'c', 'cpp',
     meson_version : '>= 0.40',
-    version : '0.1',
+    version : run_command('utils/gen-version.sh',
+                          '@0@'.format(meson.source_root()),
+                          check : true).stdout().strip(),
     default_options : [
         'werror=true',
         'warning_level=2',
@@ -8,11 +10,6 @@ project('libcamera', 'c', 'cpp',
     ],
     license : 'LGPL 2.1+')
 
-# TODO: Extract this from project.version.
-#       Ideally the version at Documentation/conf.py should be
-#       generated from this too.
-api_version = '0.1'
-
 cc = meson.get_compiler('c')
 config_h = configuration_data()
 
diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp
index cf881ce2..c5da46b4 100644
--- a/src/libcamera/camera_manager.cpp
+++ b/src/libcamera/camera_manager.cpp
@@ -9,6 +9,7 @@
 
 #include <libcamera/camera.h>
 #include <libcamera/event_dispatcher.h>
+#include <libcamera/version.h>
 
 #include "device_enumerator.h"
 #include "event_dispatcher_poll.h"
@@ -26,6 +27,11 @@ namespace libcamera {
 LOG_DEFINE_CATEGORY(Camera)
 
 /**
+ * \brief The library global version string
+ */
+const std::string version(LIBCAMERA_VERSION);
+
+/**
  * \class CameraManager
  * \brief Provide access and manage all cameras in the system
  *
@@ -79,6 +85,8 @@ int CameraManager::start()
 	if (enumerator_)
 		return -EBUSY;
 
+	LOG(Camera, Info) << "libcamera " << version;
+
 	enumerator_ = DeviceEnumerator::create();
 	if (!enumerator_ || enumerator_->enumerate())
 		return -ENODEV;
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 8075b1f6..336f4f06 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -80,6 +80,7 @@ control_types_cpp = custom_target('control_types_cpp',
 libcamera_sources += control_types_cpp
 
 libcamera_deps = [
+    declare_dependency(sources : version_h),
     cc.find_library('dl'),
     libudev,
 ]
diff --git a/utils/gen-version.sh b/utils/gen-version.sh
new file mode 100755
index 00000000..b3003d7a
--- /dev/null
+++ b/utils/gen-version.sh
@@ -0,0 +1,37 @@
+#!/bin/sh
+
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Generate a version string using git describe
+
+if [ -n "$1" ]
+then
+	cd "$1" 2>/dev/null || exit 1
+fi
+
+# Get a short description from the tree.
+version=$(git describe --abbrev=8 --match "v[0-9]*" 2>/dev/null)
+
+if [ -z "$version" ]
+then
+	# Handle an un-tagged repository
+	sha=$(git describe --abbrev=8 --always 2>/dev/null)
+	commits=$(git log --oneline | wc -l 2>/dev/null)
+	version=v0.0.$commits.$sha
+fi
+
+# Prevent changed timestamps causing -dirty labels
+git update-index --refresh > /dev/null 2>&1
+dirty=$(git diff-index --name-only HEAD 2>/dev/null) || dirty=
+
+# Strip the 'g', and replace the preceeding '-' with a '+' to denote a label
+version=$(echo "$version" | sed -e 's/-g/+/g')
+
+# Fix the '-' (the patch count) to a '.' as a version increment.
+version=$(echo "$version" | sed -e 's/-/./g')
+
+if [ -n "$dirty" ]
+then
+	version=$version-dirty
+fi
+
+echo "$version"