Fix several small bugs that an AI agent detected

[mjcheetham]

A collection of small bug fixes found with the help of an AI agent scanning the codebase. None of these are known to be actively exploited or causing user-reported issues, but each is a latent defect that could cause crashes, hangs, or incorrect behaviour under the right conditions.

Fixes

Credential UI — github/gitlab: use correct param order

• Custom credential UI commands had swapped URL and username arguments.

Stream extensions — streamextensions: fix a bug in multi-var reset handling

• Multi-dictionary writer emitted the wrong value when a reset marker was followed by a single entry.

GitHub auth — github: handle empty domain or enterprise hints

• Null-reference exception when WWW-Authenticate header is missing domain/enterprise hints.

GitHub account filtering — github: do not filter accounts outside of dotcom

• Account filtering was applied outside of GitHub.com despite detecting it shouldn't be.

Network diagnostics — diagnose: fix network diag to await HTTP requests

• HTTP requests in the network diagnostic were not properly awaited.

macOS notarize script — macos: add die function to notarize.sh script

• Missing die function.

Git stderr handling — git: drain stderr on IsInsideRepository

• Potential hang when Git writes enough to stderr to fill the pipe buffer.

Windows layout script — windows: fix layout.ps1 if symboloutput is not set

• Null-reference trimming SymbolOutput when the variable is unset.

OAuth device code UI — oauth: pass cancellation token to in-proc device code UI

• Cancellation token was not forwarded, so dismissing the dialog didn't work.

TRACE2 thread ID — trace2: fix main thread identification

• Main thread ID starts at 1, not 0.

TRACE2 perf format — trace2: fix crash in perf format for large elapsed times

• ArgumentOutOfRangeException crash when elapsed time exceeds 9999 seconds.

HTTP config — http: use correct http.sslAutoClientCert setting name

• Setting was read from the wrong Git config section.

TRACE2 writer cleanup — trace2: fix incomplete disposal of writers on cleanup

• Forward iteration with removal skipped every other writer, leaking file handles.

Git stderr redirect — git: fix crash when reading stderr from non-redirected processes

• InvalidOperationException when GetRemotes/CreateGitException read non-redirected stderr.

Executable lookup — environment: check execute permission in TryLocateExecutable

• PATH scan didn't verify execute bits on POSIX, unlike the which it replaced.

Installer Exec command — windows: fix en-dash characters in installer Exec command

• Unicode en-dash characters instead of ASCII hyphens broke PowerShell 5.1 parameter parsing.

[Copilot]

Pull request overview

This PR batches a set of targeted latent bug fixes across authentication/UI helpers, TRACE2 logging, Git process handling, networking diagnostics, installer scripts, and executable discovery to prevent crashes/hangs and correct subtle behavioral issues.

Changes:

• Fix argument ordering, cancellation propagation, and account filtering edge cases in GitHub/GitLab auth and credential UI flows.
• Improve reliability in core utilities (TRACE2 formatting/disposal/thread naming, stream dictionary writer, Git config lookup, network diagnostic awaiting).
• Harden platform tooling and process handling (drain/redirect stderr, executable permission checks on POSIX, installer/notarize scripts, PowerShell command formatting).

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/windows/Installer.Windows/layout.ps1	Guard SymbolOutput trimming when unset to avoid null-reference.
src/windows/Installer.Windows/Installer.Windows.csproj	Replace Unicode en-dash with ASCII hyphen in PowerShell args.
src/shared/TestInfrastructure/Objects/TestFileSystem.cs	Add executable-bit simulation for POSIX tests (FileIsExecutable, SetExecutable).
src/shared/GitLab/UI/Commands/CredentialsCommand.cs	Fix handler parameter order for URL/username.
src/shared/GitHub/UI/Commands/CredentialsCommand.cs	Fix handler parameter order for enterprise URL/username.
src/shared/GitHub/GitHubHostProvider.cs	Ensure account filtering is skipped outside GitHub.com.
src/shared/GitHub/GitHubAuthChallenge.cs	Attempt to null-proof GetHashCode() for missing domain/enterprise hints.
src/shared/Core/Trace2Message.cs	Prevent perf-format padding logic from crashing on large elapsed values.
src/shared/Core/Trace2.cs	Fix TRACE2 writer cleanup (reverse iteration) and “main” thread identification.
src/shared/Core/StreamExtensions.cs	Fix multi-dictionary writer emitting wrong value after reset marker.
src/shared/Core/Settings.cs	Read http.sslAutoClientCert from the correct Git config section.
src/shared/Core/Git.cs	Reduce hang/crash risk by draining/redirecting stderr in specific flows.
src/shared/Core/FileSystem.cs	Add FileIsExecutable API + POSIX execute-bit check implementation.
src/shared/Core/EnvironmentBase.cs	Respect execute permission when locating executables on POSIX PATH.
src/shared/Core/Diagnostics/NetworkingDiagnostic.cs	Await HTTP diagnostic requests; avoid async void helper.
src/shared/Core/Authentication/OAuthAuthentication.cs	Pass cancellation token through to in-proc device code UI.
src/shared/Core.Tests/Trace2MessageTests.cs	Add coverage for large elapsed time formatting.
src/shared/Core.Tests/StreamExtensionsTests.cs	Add regression coverage for reset+single-entry write behavior.
src/shared/Core.Tests/EnvironmentTests.cs	Add tests ensuring non-executable matches are skipped on POSIX.
src/shared/Core.Tests/Commands/DiagnoseCommandTests.cs	Update tests to await async HTTP helper and remove async void usage.
src/osx/Installer.Mac/notarize.sh	Add missing die helper function.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Reading StandardOutput.ReadToEnd() and only then draining StandardError does not fully eliminate the deadlock/hang risk when both streams are redirected: the child process can block on a full stderr pipe before it closes stdout, causing ReadToEnd() on stdout to wait forever. To reliably prevent hangs, drain stdout and stderr concurrently (e.g., start both ReadToEndAsync() tasks before waiting for exit, or use async event-based reads).

Suggested change

	string data = git.StandardOutput.ReadToEnd();
	// Read all of standard error to prevent the process from hanging if it writes enough data to fill the buffer
	if (suppressStreams)
	{
	git.StandardError.ReadToEnd();
	}
	Task<string> standardOutputTask = git.StandardOutput.ReadToEndAsync();
	Task<string> standardErrorTask = suppressStreams
	? git.StandardError.ReadToEndAsync()
	: Task.FromResult(string.Empty);
	Task.WhenAll(standardOutputTask, standardErrorTask).GetAwaiter().GetResult();
	string data = standardOutputTask.GetAwaiter().GetResult();