Replace build date with Git hash and commit date

The usage of a build date prevents reproducible builds.

wscript

@@ -9,8 +9,6 @@ path.append(abspath('common'))
 import waflib
 import waf as docs_waf
 
-version = '5.0.0 (master)'
-
 build_all = ['user',
              'rsb',
              'c-user',
@@ -31,7 +29,6 @@ def options(opt):
     docs_waf.cmd_options(opt)
 
 def configure(conf):
-    conf.env.VERSION = version
     for b in building:
         conf.recurse(b)
     conf.env['BUILD_FROM_TOP'] = 'yes'
@@ -53,7 +50,43 @@ def coverpage_js(ctx):
     with open(ctx.outputs[0].abspath(), 'w') as o:
         o.write(js.replace('@CATALOGUE', xml))
 
+def pretty_day(day):
+    if day == 3:
+        s = 'rd'
+    elif day == 11:
+        s = 'th'
+    elif day == 12:
+        s = 'th'
+    elif day == 13:
+        s = 'th'
+    elif day % 10 == 1:
+        s = 'st'
+    elif day % 10 == 2:
+        s = 'nd'
+    else:
+        s = 'th'
+    return str(day) + s
+
 def build(ctx):
+    #
+    # Get date and version from Git
+    #
+    version = '5.0.0'
+    if ctx.exec_command(['git', 'diff-index', '--quiet', 'HEAD']) == 0:
+        modified = ''
+    else:
+        modified = '-modified'
+    try:
+        out = ctx.cmd_and_log(['git', 'log', '-1', '--format=%H,%cd', '--date=format:%e,%B,%Y'])
+        f = out.strip('\n').split(',')
+        version = version + '.' + f[0] + modified
+        date = pretty_day(int(f[1])) + ' ' + f[2] + ' ' + f[3]
+    except waflib.Build.Errors.WafError:
+        date = 'unknown date'
+    ctx.env.DATE = date
+    ctx.env.RELEASE = version + ' (' + date + ')'
+    ctx.env.VERSION = version
+
     #
     # Generate any PlantUML images if enabled.
     #