propagate locale settings with option --WSL (mintty/wsltty#259)

docs/mintty.1

@@ -298,6 +298,8 @@ otherwise, it refers to the installed WSL packages as listed by the
 Windows tool \fBwslconfig /l\fP or \fBwsl -l\fP.
 Implies \fB--wsl -o Locale=C -o Charset=UTF-8\fP, \fB--rootfs=\fP..., 
 and \fB--icon=\fP... if a respective icon file exists for the distribution.
+Also sets up the gateway to propagate locale settings LANG, LC_CTYPE, LC_ALL 
+and environment variable APPDATA to the WSL session.
 
 .TP
 \fB--WSLmode\fP \fIWSL DISTRIBUTION NAME\fP

src/winmain.c

@@ -4992,6 +4992,7 @@ main(int argc, char *argv[])
 #ifdef wslbridge2
     argc += start_home;
 #endif
+    argc += 6;  // LANG, LC_CTYPE, LC_ALL
 
     char ** new_argv = newn(char *, argc + 8 + start_home + (wsltty_appx ? 2 : 0));
     char ** pargv = new_argv;
@@ -5029,6 +5030,12 @@ main(int argc, char *argv[])
 #endif
     *pargv++ = "-e";
     *pargv++ = "APPDATA";
+    *pargv++ = "-e";
+    *pargv++ = "LANG";
+    *pargv++ = "-e";
+    *pargv++ = "LC_CTYPE";
+    *pargv++ = "-e";
+    *pargv++ = "LC_ALL";
     if (start_home) {
 #ifdef wslbridge2
       *pargv++ = "--wsldir";

wiki/Changelog.md

@@ -6,6 +6,9 @@ Window handling
   * Keep hotkey-started window in taskbar (#1035).
   * Override font zooming also with Ctrl, to support FancyZones (#487).
 
+Character encoding
+  * Propagate locale settings with option --WSL (mintty/wsltty#259).
+
 ### 3.4.0 (19 September 2020) ###
 
 Window handling / Tabs