fix: handle unbound BASH_SOURCE when install.sh is piped via curl

[ericksoa]

Summary

curl -fsSL https://www.nvidia.com/nemoclaw.sh | bash fails with BASH_SOURCE[0]: unbound variable because BASH_SOURCE is empty when piped and set -u treats it as unbound.

Fix: ${BASH_SOURCE[0]:-$0} falls back to $0 when BASH_SOURCE is unset.

Regression from #470.

Closes #655

Summary by CodeRabbit

• Bug Fixes
  • Improved installation script reliability across different shell environments.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

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Run ID: d94ba07d-8466-49b3-9e9b-807245eac440

📥 Commits

Reviewing files that changed from the base of the PR and between 2ce2905 and d76cc4c.

📒 Files selected for processing (1)

• install.sh

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📝 Walkthrough

Walkthrough

The install.sh script now handles the case where BASH_SOURCE[0] is unset or empty by using a fallback to $0. This allows the script to execute correctly when piped via curl | bash without triggering an unbound variable error.

Changes

Cohort / File(s)	Summary
Script Directory Resolution install.sh	Added fallback mechanism to BASH_SOURCE[0]:-$0 to resolve script directory, preventing unbound variable errors when script is piped via curl.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A hop, a skip, a bash variable fix,
When piped through curl, it's all about tricks,
With $0 as backup, we're set to succeed,
This little fallback is all that we need!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main fix: handling an unbound BASH_SOURCE variable when install.sh is piped via curl, which is the core change in this PR.
Linked Issues check	✅ Passed	The PR implements the exact fix proposed in issue #655 by using ${BASH_SOURCE[0]:-$0} fallback syntax to resolve SCRIPT_DIR when BASH_SOURCE is unset, directly addressing the regression from PR #470.
Out of Scope Changes check	✅ Passed	The change is narrowly scoped to the install.sh script and only modifies the SCRIPT_DIR computation to handle the unbound variable issue, with no unrelated alterations present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/install-bash-source-piped

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