This concerns the behavior when running an external command from a key
binding. The history is:
Prior to 5f16a299a7, fish would run these external commands in shell
modes. This meant that fish would pick up any tty changes from external
commands (see #2114).
After 5f16a299a7, fish would save and restore its shell modes around
these external commands. This introduced a regression where anything the
user typed while a bound external command was executing would be echoed,
because external command mode has ECHO set in c_lflag. (This can be
reproed easily with `bind -q 'sleep 1'` and then pressing q and typing).
So 5f16a299a7 was reverted in fd9355966.
This commit partially reverts fd9355966. It has it both ways: external
commands are launched with shell modes, but/and shell modes are restored
after the external command completes. This allows commands to muck with
the tty, as long as they can handle getting shell modes; but it does not
enable ECHO mode so it fixes the regression found in #7770.
Fixes#7770. Fixes#2114 (for the third time!)
This partially reverts commit fd9355966e.
3cb105adbd