[config] Change the way to select the CONFIG_SHELL

Transform the single boolean option to a 'choice' selection
with two options: "sh" and "ash".

This is needed to later add "bash" as override.

1 files changed, 39 insertions, 9 deletions

diff --git a/config/global/build-behave.in b/config/global/build-behave.in
index 7f8a854a..2fb1a298 100644
--- a/config/global/build-behave.in
+++ b/config/global/build-behave.in
@@ -44,16 +44,46 @@ config USE_PIPES
       Use gcc's option -pipe to use pipes rather than temp files when building
       the toolchain.
 
-config CONFIG_SHELL_ASH
+choice
+    bool
+    prompt "Shell to use as CONFIG_SHELL"
+    default CONFIG_SHELL_SYSTEM
+
+config CONFIG_SHELL_SH
     bool
-    prompt "Use 'ash' as CONFIG_SHELL"
-    default n
+    prompt "sh (the system shell)"
     help
-      Use /bin/ash as the shell used by ./configure scripts.
+      Use 'sh' as CONFIG_SHELL.
       
-      ./configure scripts make intensive use of calling a sub-shell, and the
-      traditional bash is slow, whereas ash is faster.
+      ./configure scripts and Makefiles make intensive use of calling
+      sub-shells. This is usually done by calling /bin/sh. /bin/sh ought
+      to be an at-least-POSIX-conformant shell (that is, able to interpret
+      POSIX shell scripts).
       
-      Saying 'y' here should be safe enough, but some components may not
-      accept using a shell other than bash (this is most probably true for
-      old versions). If you have trouble, say 'n' here and see if it fixes it.
+      On many (most?) systems, /bin/sh is a symlink to bash. On some other
+      systems (eg. Ubuntu, latest Debian), /bin/sh points to dash (or ash).
+      bash is a full-featured shell, with many extension to POSIX, but is
+      quite slow (see ection BUGS in the bash man page), while dash is
+      faster, with very few extensions to POSIX.  On the other hand, some
+      ./configure scripts, although written to use /bin/sh, may really
+      require to be run by bash.
+      
+      The default is to use your system's /bin/sh shell. If you want to
+      run faster, you can select to use dash. If you have problems with
+      either the system shell or when using dash, then you can force to
+      use bash.
+      
+config CONFIG_SHELL_ASH
+    bool
+    prompt "ash"
+    help
+      Use 'ash' as CONFIG_SHELL.
+      
+      See help for CONFIG_SHELL_SH, above, for more explanations.
+
+endchoice
+
+config CONFIG_SHELL
+    string
+    default "sh"    if CONFIG_SHELL_SH
+    default "ash"   if CONFIG_SHELL_ASH