Bash 5.1: Make shell_script_filename available to startup files

[Marc Aurèle La France]

Currently, only the script's arguments are passed as positional 
parameters.  For compatibility reasons, $0 cannot be used to also pass the 
script's filename, so I'm creating a new BASH_SCRIPT variable instead.

Below is a heavily simplified test case.  The goal is to stop it from 
asking who you are.

Documentation changes included.

Please Reply-To-All.

Thanks.

Marc.

--

In an empty directory, first run ...

#! /bin/sh

rm -fr BASH_ENV bash_env

cat > BASH_ENV <<"HERE"
{
 echo --------------------------------------------------
 echo In ${BASH_SOURCE[0]}...
 echo $0 "$@"
 set
 echo --------------------------------------------------
} |
 tee /dev/fd/2 |
 grep -q bash_env ||
 echo 'Who are you?'
HERE

ln -f BASH_ENV bash_env

exit 0

... then, in the same directory, run (case matters) ...

BASH_ENV=BASH_ENV $where_your_test_bash_is ./bash_env

--
--- bash-5.1/doc/bash.1
+++ devel-5.1/doc/bash.1
@@ -1610,6 +1610,11 @@ matching the entire regular expression.
 The element with index \fIn\fP is the portion of the
 string matching the \fIn\fPth parenthesized subexpression.
 .TP
+.B BASH_SCRIPT
+The name of the script currently being executed by \fBbash\fP, as specified on 
+the command line.
+This is set before any startup files are executed for the script.
+.TP
 .B BASH_SOURCE
 An array variable whose members are the source filenames
 where the corresponding shell function names in the
--- bash-5.1/doc/bashref.texi
+++ devel-5.1/doc/bashref.texi
@@ -5810,6 +5810,11 @@ matching the entire regular expression.
 The element with index @var{n} is the portion of the
 string matching the @var{n}th parenthesized subexpression.

+@item BASH_SCRIPT
+The name of the script currently being executed by bash, as specified on
+the command line.  This is set before any startup files are executed for
+the script.
+
 @item BASH_SOURCE
 An array variable whose members are the source filenames where the
 corresponding shell function names in the @code{FUNCNAME} array
--- bash-5.1/shell.c
+++ devel-5.1/shell.c
@@ -686,6 +686,7 @@ main (argc, argv, env)
   else if (arg_index != argc && read_from_stdin == 0)
     {
       shell_script_filename = argv[arg_index++];
+      bind_variable ("BASH_SCRIPT", shell_script_filename, 0);
       arg_index = bind_args (argv, arg_index, argc, 1);        /* $1 ... $n */
     }
   else