i18n: make sure 'en' in Accept-Language is recognized as having 100% coverage - i18n.lang is for source language

https://github.com/cdent/paste/blob/3.2.3/paste/wsgiwrappers.py#L89 describes
how paste solved the problem. TG solves the same problem (with less
explanation) in
https://github.com/TurboGears/tg2/blob/tg2.4.2/tg/request_local.py#L36 with
fallback language specified in i18n.lang .

Thus, clarify the use of i18n.lang (refining f2f7a8c1281e and 8931078f70db) and
set 'en' as default value on app startup.

TurboGears requires an (empty) translation for the source language which is
default for i18n.lang . The empty .mo for en is created as the 4 magic .mo
bytes followed by lengths of 0:
  printf '\x95\x04\x12\xde\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0' > kallithea/i18n/en/LC_MESSAGES/kallithea.mo

Based on report and analysis by Wolfgang Scherer. Also discussed upstream on
https://github.com/TurboGears/tg2/pull/115 .

development.ini

@@ -90,10 +90,12 b' full_stack = true'
 static_files = true
 
 ## Internationalization (see setup documentation for details)
-## By default, the language requested by the browser is used if available.
-#i18n.enabled = false
-## Fallback language, empty for English (valid values are the names of subdirectories in kallithea/i18n):
-i18n.lang =
+## By default, the languages requested by the browser are used if available, with English as default.
+## Set i18n.enabled=false to disable automatic language choice.
+#i18n.enabled = true
+## To Force a language, set i18n.enabled=false and specify the language in i18n.lang.
+## Valid values are the names of subdirectories in kallithea/i18n with a LC_MESSAGES/kallithea.mo
+#i18n.lang = en
 
 cache_dir = %(here)s/data
 index_dir = %(here)s/data/index

docs/setup.rst

@@ -80,13 +80,12 b' The Kallithea web interface is automatic'
 language, as indicated by the browser. Thus, different users may see the
 application in different languages. If the requested language is not available
 (because the translation file for that language does not yet exist or is
-incomplete), the language specified in setting ``i18n.lang`` in the Kallithea
-configuration file is used as fallback. If no fallback language is explicitly
-specified, English is used.
+incomplete), English is used.
 
 If you want to disable automatic language detection and instead configure a
 fixed language regardless of user preference, set ``i18n.enabled = false`` and
-set ``i18n.lang`` to the desired language (or leave empty for English).
+specify another language by setting ``i18n.lang`` in the Kallithea
+configuration file.
 
 
 Using Kallithea with SSH

kallithea/config/app_cfg.py

@@ -98,6 +98,11 b' class KallitheaAppConfig(AppConfig):'
         # Disable transaction manager -- currently Kallithea takes care of transactions itself
         self['tm.enabled'] = False
 
+        # Set the i18n source language so TG doesn't search beyond 'en' in Accept-Language.
+        # Don't force the default here if configuration force something else.
+        if not self.get('i18n.lang'):
+            self['i18n.lang'] = 'en'
+
 
 base_config = KallitheaAppConfig()
 

kallithea/lib/paster_commands/template.ini.mako

@@ -185,10 +185,12 b' full_stack = true'
 static_files = true
 
 <%text>## Internationalization (see setup documentation for details)</%text>
-<%text>## By default, the language requested by the browser is used if available.</%text>
-#i18n.enabled = false
-<%text>## Fallback language, empty for English (valid values are the names of subdirectories in kallithea/i18n):</%text>
-i18n.lang =
+<%text>## By default, the languages requested by the browser are used if available, with English as default.</%text>
+<%text>## Set i18n.enabled=false to disable automatic language choice.</%text>
+#i18n.enabled = true
+<%text>## To Force a language, set i18n.enabled=false and specify the language in i18n.lang.</%text>
+<%text>## Valid values are the names of subdirectories in kallithea/i18n with a LC_MESSAGES/kallithea.mo</%text>
+#i18n.lang = en
 
 cache_dir = %(here)s/data
 index_dir = %(here)s/data/index