install: guard against duplicate PATH entries on reinstall

[marcelsafin]

Running the installer twice without restarting the shell causes the PATH configuration line to be appended to the shell profile a second time. This happens because the script checks command -v copilot to decide whether to prompt for PATH setup, but that check requires a shell restart to reflect the previous install's RC_FILE changes.

Repro:

curl -fsSL https://gh.io/copilot-install | bash   # say y to PATH prompt
curl -fsSL https://gh.io/copilot-install | bash   # say y again → duplicate line

Result: ~/.bash_profile (or equivalent) contains the same export PATH=... line twice.

This adds a grep -qF check for the exact PATH_LINE in RC_FILE before appending, making the write idempotent. On reinstall, the script reports that the configuration is already present instead of duplicating it.

Before (reinstall):

✓ Added PATH configuration to /home/user/.bash_profile   ← duplicate appended

After (reinstall):

✓ PATH configuration already in /home/user/.bash_profile

Works for all shells (bash, zsh, fish, POSIX fallback) since it matches the exact PATH_LINE string.

[Copilot]

Pull request overview

This PR makes the installer’s PATH configuration step idempotent by checking whether the intended PATH export line is already present in the selected shell profile before appending it, preventing duplicate entries when re-running the installer in the same shell session.

Changes:

• Add a grep -qF presence check for PATH_LINE in RC_FILE before appending.
• Print a distinct message when PATH configuration is already present instead of writing again.

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[Copilot]

grep -qF matches the PATH_LINE as a substring anywhere in the file. That can produce a false positive (e.g., if the line exists but is commented out or appears inside another longer line), causing the installer to claim PATH is configured when it isn’t. If the intent is to match the exact line that the script appends, use a full-line fixed-string match (e.g., grep -qxF) and consider adding -- before the pattern for safety.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

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[Copilot]

If mkdir -p or the append to $RC_FILE fails (permissions, read-only FS), the script will still print a success message. Consider checking the return status and emitting an error / non-zero exit so users aren’t told PATH was configured when it wasn’t.