Configure Git Bash shell profiles during Windows install

[svarlamov]

Configure Git Bash shell profiles during Windows install

Summary

Fixes #517. Git Bash (MSYS2/MinGW) prepends /mingw64/bin to PATH during its own shell initialization, which shadows the git-ai shim even when the Windows PATH has been correctly set by Set-PathPrependBeforeGit. This adds a new section to install.ps1 that writes export PATH="$HOME/.git-ai/bin:$PATH" into the user's ~/.bashrc or ~/.bash_profile, mirroring what install.sh already does for Unix shells.

The new block:

1. Detects Git for Windows by checking common install paths (Program Files, Program Files (x86), LocalAppData\Programs)
2. Finds existing .bashrc or .bash_profile (or creates .bashrc if neither exists)
3. Checks for an existing .git-ai/bin marker to avoid duplicate entries
4. Appends the PATH export if not already present
5. Wraps everything in try/catch so a failure here never blocks the rest of the install

Updates since last revision

• Fixed UTF-8 BOM issue flagged by Devin Review: replaced Add-Content -Encoding UTF8 with [System.IO.File]::AppendAllText() using UTF8Encoding($false) to avoid writing a BOM that would cause command not found errors in bash on PowerShell 5.1.

Review & Testing Checklist for Human

• Test on a real Windows machine with Git Bash installed — this change is entirely in PowerShell and cannot be verified by the Rust test suite or Linux CI. Run the installer, then open Git Bash and confirm which git resolves to ~/.git-ai/bin/git (not /mingw64/bin/git)
• Verify no UTF-8 BOM in created .bashrc — the code now uses UTF8Encoding($false) + AppendAllText, but confirm the written file has no BOM bytes (EF BB BF) at the start, especially when .bashrc is newly created (no pre-existing file)
• Test idempotency — run the installer twice and confirm the PATH export is not duplicated in .bashrc
• Test with no existing .bashrc — confirm the installer creates .bashrc and the export line is correct. Consider whether creating .bashrc when a user has never used Git Bash is desirable, or if this should only append to existing files

Notes

• Git Bash detection only covers standard Git for Windows install paths. Custom locations (Scoop, Chocolatey portable, etc.) won't be detected, but the code simply skips configuration in that case — no harm done.
• Link to Devin run
• Requested by @svarlamov

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[svarlamov]

review devin feedback

[devin-ai-integration]

Devin Review found 1 new potential issue.

View 8 additional findings in Devin Review.

[devin-ai-integration]

🟡 Eager Join-Path evaluation with null env var aborts entire Git Bash config block

If ${env:ProgramFiles(x86)} is $null (e.g., on 32-bit Windows), the Join-Path call on line 453 throws a ParameterBindingValidationException during array construction, before the loop on line 456 ever executes. This causes the entire try block to jump to catch, skipping Git Bash configuration entirely — even if Git Bash is installed at one of the other checked paths ($env:ProgramFiles\Git\bin\bash.exe or $env:LOCALAPPDATA\Programs\Git\bin\bash.exe).

Root Cause

All three Join-Path calls on lines 452-454 are evaluated eagerly when constructing the $gitForWindowsPaths array. The null-guard $p -and on line 457 was intended to handle null paths, but it never gets reached because the exception occurs during array initialization.

$gitForWindowsPaths = @(
    (Join-Path $env:ProgramFiles 'Git\bin\bash.exe'),
    (Join-Path ${env:ProgramFiles(x86)} 'Git\bin\bash.exe'),  # throws if null
    (Join-Path $env:LOCALAPPDATA 'Programs\Git\bin\bash.exe')
)

With Set-StrictMode -Version Latest (line 2), Join-Path with a $null -Path parameter throws a terminating error. The fix is to guard each path construction against null, e.g., by only adding non-null paths to the array, or by using if checks before Join-Path.

Impact: On 32-bit Windows (rare but possible), Git Bash shell profile configuration is silently skipped with only a warning message, even when Git Bash is installed.

Suggested change

	$gitForWindowsPaths = @(
	(Join-Path $env:ProgramFiles 'Git\bin\bash.exe'),
	(Join-Path ${env:ProgramFiles(x86)} 'Git\bin\bash.exe'),
	(Join-Path $env:LOCALAPPDATA 'Programs\Git\bin\bash.exe')
	)
	$gitForWindowsPaths = @()
	if ($env:ProgramFiles) { $gitForWindowsPaths += Join-Path $env:ProgramFiles 'Git\bin\bash.exe' }
	if (${env:ProgramFiles(x86)}) { $gitForWindowsPaths += Join-Path ${env:ProgramFiles(x86)} 'Git\bin\bash.exe' }
	if ($env:LOCALAPPDATA) { $gitForWindowsPaths += Join-Path $env:LOCALAPPDATA 'Programs\Git\bin\bash.exe' }

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