fix(xonsh): Ignore empty $ATUIN_HISTORY_ID in postcommand

[nahoj]

This PR makes xonsh behavior consistent with other shells: atuin history end should ignore $ATUIN_HISTORY_ID being undefined OR empty.

$ATUIN_HISTORY_ID can be empty if atuin history start fails, which happened to me in #3561.

Checks

• I am happy for maintainers to push small adjustments to this PR, to speed up the review cycle
• I have checked that there are no existing pull requests for the same thing

[github-actions]

Fossier: Manual Review Requested

@nahoj is a new contributor. A maintainer should review this PR before merging.

Score Breakdown

Total Score: 53.2/100 | Confidence: 100% | Outcome: REVIEW

Signal	Value	Score	Weight
account_age	5721	1.00	0.09
public_repos	44	1.00	0.05
contribution_history	46	0.23	0.05
follower_ratio	5.0	1.00	0.05
bot_signals	False	0.50	0.04
open_prs_elsewhere	13	0.00	0.09
closed_prs_elsewhere	13	0.00	0.10
merged_prs_elsewhere	34	1.00	0.08
prior_interaction	0	0.00	0.08
activity_velocity	2	0.67	0.08
pr_content	...	0.70	0.08
commit_email	no_email	0.50	0.04
pr_description	...	0.70	0.05
repo_stars	30449	0.30	0.04
org_membership	0	0.20	0.03
commit_verification	...	1.00	0.04
contributor_stars	30	0.60	0.04

[greptile-apps]

Greptile Summary

Fixes the xonsh postcommand hook to skip atuin history end when $ATUIN_HISTORY_ID is empty, not just when it's undefined. The precommand already sets it to "" on failure (line 19), so the old not in check was insufficient.

• Changes "ATUIN_HISTORY_ID" not in ${...} to not ${...}.get("ATUIN_HISTORY_ID"), which treats both missing and empty-string values as falsy — aligning xonsh with the behavior of other supported shells.

Confidence Score: 5/5

Single-line guard change with no side effects; straightforward and correct.

The fix directly addresses the code path where $ATUIN_HISTORY_ID is set to "" on atuin history start failure, and using .get() with a falsy check handles both the missing-key and empty-string cases correctly.

No files require special attention.

Important Files Changed

Filename	Overview
crates/atuin/src/shell/atuin.xsh	Guard in postcommand now skips execution when ATUIN_HISTORY_ID is missing or empty, consistent with precommand setting it to "" on failure.

_{Reviews (1): Last reviewed commit: "fix(xonsh): Ignore empty $ATUIN_HISTORY_..." | Re-trigger Greptile}