build: avoid dynamic dates for reproducibility

We were using dates (in documentation, (c) notices etc) based on the
build-date; that makes it hard to do reproducible builds, so specify a
specific date in the top-level meson file, and use that throughout.

build-aux/version.texi.in

@@ -1,4 +1,5 @@
 @set UPDATED @UPDATED@
 @set UPDATED-MONTH @UPDATEDMONTH@
+@set UPDATED-YEAR @UPDATEDYEAR@
 @set EDITION @VERSION@
 @set VERSION @VERSION@

guile/mu-guile.texi

@@ -14,7 +14,7 @@
 @include version.texi
 
 @copying
-Copyright @copyright{} 2012 Dirk-Jan C. Binnema
+Copyright @copyright{} 2012-@value{UPDATED-YEAR} Dirk-Jan C. Binnema
 
 @quotation
 Permission is granted to copy, distribute and/or modify this document

man/meson.build

@@ -1,4 +1,4 @@
-## Copyright (C) 2021 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+## Copyright (C) 2021-2023 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
 ##
 ## This program is free software; you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -63,13 +63,7 @@ man_orgs=[
   'mu-view.1.org'
 ]
 
-env = environment()
-env.set('LANG', 'C')
-yearmonth = run_command('date', '+%B %Y', check:true, capture:true, env: env)
-ym=yearmonth.stdout().strip()
-
 foreach src : man_orgs
-
   # meson makes in tricky to use the results of e.g. configure_file
   # in custom_commands..., so this is admittedly a little hacky.
   org = join_paths(meson.current_build_dir(), src)
@@ -81,15 +75,14 @@ foreach src : man_orgs
   #  @MAN_DATE@: date of the generation (not yet supported by ox-man)
   conf_data = configuration_data()
   conf_data.set('SECTION_ID', section)
-  conf_data.set('MAN_DATE', ym)
+  conf_data.set('MAN_DATE', mu_month_year)
   configure_file(input: src, output:'@BASENAME@.org',
                  configuration: conf_data)
 
   expr_tmpl = ''.join([
     '(progn',
     '  (require \'ox-man)',
-    '  (org-export-to-file \'man "@0@"))',
-  ])
+    '  (org-export-to-file \'man "@0@"))'])
   expr = expr_tmpl.format(org.substring(0,-4))
   sectiondir = join_paths(mandir, 'man' + section)
 

meson.build

@@ -24,9 +24,11 @@ project('mu', ['c', 'cpp'],
           'buildtype=debugoptimized',
           'warning_level=3',
           'c_std=c11',
-          'cpp_std=c++17'
-        ]
-       )
+          'cpp_std=c++17'])
+
+# hard-code the date here (for reproduciblity); we derive the dates used in e.g.
+# documentation from this.
+mu_date='2023-10-14'
 
 # installation paths
 prefixdir = get_option('prefix')
@@ -42,7 +44,6 @@ else
   mu4e_lispdir= get_option('lispdir') / 'mu4e'
 endif
 
-
 ################################################################################
 # compilers / flags
 #
@@ -97,6 +98,22 @@ endforeach
 # https://github.com/djcb/mu/issues/2347
 cxx.check_header('charconv', required:true)
 
+
+################################################################################
+# derived date values (based on 'mu-date'); used in docs
+date=find_program('date', required:true)
+env = environment()
+env.set('LANG', 'C')
+mu_day_month_year = run_command(date, '-u', '+%d %B %Y', '--date', mu_date,
+                                check:true, capture:true,
+                                env: env).stdout().strip()
+mu_month_year = run_command(date, '-u', '+%B %Y', '--date', mu_date,
+                            check:true, capture:true,
+                            env: env).stdout().strip()
+mu_year = run_command(date, '-u', '+%Y', '--date', mu_date,
+                      check:true, capture:true, env: env).stdout().strip()
+
+
 ################################################################################
 # config.h setup
 #
@@ -244,10 +261,11 @@ endif
 version_texi_data=configuration_data()
 version_texi_data.set('VERSION', meson.project_version())
 version_texi_data.set('EDITION', meson.project_version())
-version_texi_data.set('UPDATED',
-                      run_command('date', '+%d %B %Y', check:true).stdout().strip())
-version_texi_data.set('UPDATEDMONTH',
-                      run_command('date', '+%B %Y', check:true).stdout().strip())
+
+# derived date values
+version_texi_data.set('UPDATED', mu_day_month_year)
+version_texi_data.set('UPDATEDMONTH', mu_month_year)
+version_texi_data.set('UPDATEDYEAR', mu_year)
 
 configure_file(input: join_paths('build-aux', 'version.texi.in'),
                output: 'version.texi',

mu4e/meson.build

@@ -126,19 +126,6 @@ install_data(mu4e_srcs, install_dir: mu4e_lispdir)
 install_data('mu4e-about.org', install_dir : join_paths(datadir, 'doc', 'mu'))
 
 if makeinfo.found()
-
-  fulldate = run_command('date', '+%d %B %Y', check:true).stdout().strip()
-  monthdate = run_command('date', '+%B %Y', check:true).stdout().strip()
-  version_texi_data = configuration_data({
-    'fulldate'  : fulldate,
-    'monthdate' : monthdate,
-    'version'   : meson.project_version(),
-  })
-  version_texi = configure_file(
-    input:  'version.texi.in',
-    output: 'version.texi',
-    configuration: version_texi_data)
-
   custom_target('mu4e_info',
                 input: 'mu4e.texi',
                 output: 'mu4e.info',

mu4e/mu4e.texi

@@ -12,7 +12,7 @@
 @c %**end of header
 
 @copying
-Copyright @copyright{} 2012-2023 Dirk-Jan C. Binnema
+Copyright @copyright{} 2012-@value{UPDATED-YEAR} Dirk-Jan C. Binnema
 
 @quotation
 Permission is granted to copy, distribute and/or modify this document