Shell command in back quotes with <<

[alexr00]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem in Safe Mode: https://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
  • Followed all applicable steps in the debugging guide: https://flight-manual.atom.io/hacking-atom/sections/debugging/
  • Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
  • Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
  • Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages

Description

Tokenization is broken if script has back quotes with <<.

Steps to Reproduce

1. Create file test.sh
2. Open test.sh and paste example below

CHANGELOG=`cat << EOF
nginx ($VER-2~$REL) $REL; urgency=low

  * $VER

 -- $CONTRIB_NAME <$CONTRIB_EMAIL>  $DATE
EOF`

3. Write code below CHANGELOG.

Gist with example
All code below back quotes will be highlighted as 'shell code'.
Expected behavior:

The string and backtick related scopes will end with the closing backtick.

Even after the closing backtick these are the scopes:

string.unquoted.heredoc.shell
string.interpolated.backtick.shell
source.shell

Versions

VS Code version: Code 1.44.2 (ff915844119ce9485abfe8aa9076ec76b5300ddd, 2020-04-16T17:07:18.473Z)
OS version: Darwin x64 17.7.0

Additional Information

Originally from @psycho-coder in microsoft/vscode#96144