Add --version option to Python based tools.

Version file is generated at build time and stored as _version.py.
To support running uninstalled tools, a fallback version is included as
well. Example output of `--version` option:

```
$ for t in g-ir-{annotation-tool,scanner,doc-tool}; do $t --version; done
g-ir-annotation-tool 1.57.1
g-ir-scanner 1.57.1
g-ir-doc-tool 1.57.1
```

6 files changed, 23 insertions, 5 deletions

diff --git a/giscanner/__init__.py b/giscanner/__init__.py
index 139b5187..391d36bd 100644
--- a/giscanner/__init__.py
+++ b/giscanner/__init__.py
@@ -22,3 +22,7 @@ import os
 builddir = os.environ.get('UNINSTALLED_INTROSPECTION_BUILDDIR')
 if builddir is not None:
     __path__.append(os.path.join(builddir, 'giscanner'))
+try:
+    from ._version import __version__
+except ImportError:
+    __version__ = '0.0.0'
diff --git a/giscanner/_version.py.in b/giscanner/_version.py.in
new file mode 100644
index 00000000..4b56f5ba
--- /dev/null
+++ b/giscanner/_version.py.in
@@ -0,0 +1 @@
+__version__ = '@VERSION@'
diff --git a/giscanner/annotationmain.py b/giscanner/annotationmain.py
index b82ff818..c7be4f7c 100644
--- a/giscanner/annotationmain.py
+++ b/giscanner/annotationmain.py
@@ -28,6 +28,7 @@ import optparse
 import codecs
 from contextlib import contextmanager
 
+import giscanner
 from giscanner import message
 from giscanner.annotationparser import GtkDocCommentBlockParser, GtkDocCommentBlockWriter
 from giscanner.scannermain import (get_preprocessor_option_group,
@@ -54,7 +55,8 @@ def encode_stdout(encoding):
 
 
 def annotation_main(args):
-    parser = optparse.OptionParser('%prog [options] sources')
+    parser = optparse.OptionParser('%prog [options] sources',
+                                   version='%prog ' + giscanner.__version__)
 
     group = optparse.OptionGroup(parser, "Tool modes, one is required")
     group.add_option("-e", "--extract",
diff --git a/giscanner/docmain.py b/giscanner/docmain.py
index 3bea5421..53f5206c 100644
--- a/giscanner/docmain.py
+++ b/giscanner/docmain.py
@@ -24,8 +24,10 @@ from __future__ import print_function
 from __future__ import unicode_literals
 
 import os
+import sys
 import argparse
 
+import giscanner
 from .docwriter import DocWriter
 from .sectionparser import generate_sections_file, write_sections_file
 from .transformer import Transformer
@@ -33,7 +35,8 @@ from .transformer import Transformer
 
 def doc_main(args):
     parser = argparse.ArgumentParser()
-
+    parser.add_argument('--version', action='version',
+                      version='%(prog)s ' + giscanner.__version__)
     parser.add_argument("girfile")
     parser.add_argument("-o", "--output",
                       action="store", dest="output",
diff --git a/giscanner/meson.build b/giscanner/meson.build
index 006722d2..5a1e44c9 100644
--- a/giscanner/meson.build
+++ b/giscanner/meson.build
@@ -31,12 +31,18 @@ pkglibdir = join_paths(get_option('libdir'), meson.project_name())
 giscannerdir = join_paths(pkglibdir, 'giscanner')
 
 giscanner_built_files = []
-blank_conf = configuration_data()
+giscanner_conf_data = configuration_data()
+giscanner_conf_data.set('VERSION', meson.project_version())
+giscanner_built_files += configure_file(input: '_version.py.in',
+                                        output: '_version.py',
+                                        install : true,
+                                        install_dir : giscannerdir,
+                                        configuration: giscanner_conf_data)
 foreach f : giscanner_files
   giscanner_built_files += configure_file(input : f, output : f,
                                           install : true,
                                           install_dir : giscannerdir,
-                                          configuration : blank_conf)
+                                          configuration : giscanner_conf_data)
 endforeach
 
 install_subdir('doctemplates', install_dir: giscannerdir)
diff --git a/giscanner/scannermain.py b/giscanner/scannermain.py
index ffcb95cd..c608d04f 100755
--- a/giscanner/scannermain.py
+++ b/giscanner/scannermain.py
@@ -35,6 +35,7 @@ import sys
 import tempfile
 import platform
 
+import giscanner
 from giscanner import message
 from giscanner.annotationparser import GtkDocCommentBlockParser
 from giscanner.ast import Include, Namespace
@@ -101,7 +102,8 @@ def get_windows_option_group(parser):
 
 
 def _get_option_parser():
-    parser = optparse.OptionParser('%prog [options] sources')
+    parser = optparse.OptionParser('%prog [options] sources',
+                                   version='%prog ' + giscanner.__version__)
     parser.add_option('', "--quiet",
                       action="store_true", dest="quiet",
                       default=False,