### Motivation
Development tools like PyCharm send SIGINT before SIGKILL in case of
reload app. Saving history on SIGINT is the last chance to save history
in this case.
I understand that history will be flushed on Ctrl+C (SIGINT) but it
looks like no bad consequences of this. In addition history saving will
be more stable.
### Before
```xsh
# Development in PyCharm
xonsh --no-rc
echo cmd
# Ctrl+RR of Ctrl+DD to restart.
# Command history lost.
```
### After
```xsh
# Development in PyCharm
xonsh --no-rc
echo cmd
# Ctrl+R Ctrl+R for restart
# Command history is here.
```
Closes#2657
### Env
Use `$XONSH_HISTORY_SIGINT_FLUSH=False` to switch it off.
## For community
⬇️ **Please click the 👍 reaction instead of leaving a `+1` or 👍
comment**
---------
Co-authored-by: a <1@1.1>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
