feat: export an additional env var pointing to the location of jbang (#…

…1811)

* feat: export an env var with the location of jbang

It's *really* hard (impossible?) to find the location of the script that
launched the JVM from within jbang. It would be really useful to be able
to do that so you can run jbang again with some logic to precompute the
command line. This works really simply:

```
$ jbang --interactive
WARNING: Using incubator modules: jdk.incubator.vector, jdk.incubator.foreign
|  Welcome to JShell -- Version 17.0.7
|  For an introduction type: /help intro

jshell> System.getenv("JBANG")
$1 ==> "/home/dsyer/.sdkman/candidates/jbang/current/bin/jbang"
```

* Add JBANG_LAUNCH_CMD + tests for other env variables

* fix: check out instead of err for env results

---------

Co-authored-by: Max Rydahl Andersen <[email protected]>

itests/shellenv.feature

@@ -0,0 +1,13 @@
+Feature: env variables
+
+Scenario: JBANG_RUNTIME_SHELL available
+When command('jbang env@jbangdev JBANG')
+Then match out contains "JBANG_RUNTIME_SHELL"
+
+Scenario: JBANG_STDIN_NOTTY available
+  When command('jbang env@jbangdev JBANG')
+  Then match out contains "JBANG_STDIN_NOTTY"
+
+Scenario: JBANG_LAUNCH_CMD available
+  When command('jbang env@jbangdev JBANG')
+  Then match out contains "JBANG_LAUNCH_CMD"

src/main/scripts/jbang

@@ -220,6 +220,7 @@ fi
 ## run it using command substitution to have just the user process once jbang is done
 export JBANG_RUNTIME_SHELL=bash
 export JBANG_STDIN_NOTTY=$([ -t 0 ] && echo "false" || echo "true")
+export JBANG_LAUNCH_CMD=$0
 output=$(CLICOLOR_FORCE=1 "${JAVA_EXEC}" ${JBANG_JAVA_OPTIONS} -classpath "${jarPath}" dev.jbang.Main "$@")
 err=$?
 if [ $err -eq 255 ]; then

src/main/scripts/jbang.cmd

@@ -63,6 +63,7 @@ if not exist "%TDIR%" ( mkdir "%TDIR%" )
 set tmpfile=%TDIR%\%RANDOM%.jbang.tmp
 rem execute jbang and pipe to temporary random file
 set JBANG_RUNTIME_SHELL=cmd
+set JBANG_LAUNCH_CMD=%~nx0
 2>nul >nul timeout /t 0 && (set JBANG_STDIN_NOTTY=false) || (set JBANG_STDIN_NOTTY=true)
 set "CMD=!JAVA_EXEC!"
 SETLOCAL DISABLEDELAYEDEXPANSION

src/main/scripts/jbang.ps1

@@ -167,6 +167,7 @@ if ($JAVA_EXEC -eq "") {
 
 $env:JBANG_RUNTIME_SHELL="powershell"
 $env:JBANG_STDIN_NOTTY=$MyInvocation.ExpectingInput
+$env:JBANG_LAUNCH_CMD = $PSCommandPath
 $output = & "$JAVA_EXEC" $env:JBANG_JAVA_OPTIONS -classpath "$jarPath" dev.jbang.Main @args
 $err=$LASTEXITCODE