fix(git): use configured push target for Push and Sync

[AbdelrahmanHafez]

Fixes #137686, fixes #182510, fixes #158644

The issue was that the Git extension was treating the upstream branch as the push target. For a local branch named feature that tracks upstream/main, VS Code would explicitly run the equivalent of:

git push upstream feature:main

That bypasses Git's normal push destination logic. In practice that means VS Code could ignore push.default=simple, push.default=current, remote.pushDefault, and triangular workflow config, and it could push a feature branch into main even though plain git push would either push somewhere else or refuse.

I've been personally burned by this multiple times where I had to revert PRs accidentally merged to main while working on git worktrees on other branches.

This PR:

• stops constructing HEAD.name:HEAD.upstream.name for the regular Push command
• keeps the Sync pull side explicit, since upstream is still the pull/rebase source
• lets Git decide the push target for the push half of Sync by running push without an explicit remote/refspec
• stops using the upstream remote's read-only state to decide whether Sync can push, because the configured push remote can be different from the upstream remote
• updates the Sync confirmation and status tooltip copy so they no longer claim pushes go to the upstream branch
• adds Git integration tests for push.default=current, remote.pushDefault, and a read-only upstream remote with a configured push remote

This does not change explicit push commands like Push To, Publish Branch, Push Tags, or commands where the user explicitly picked a remote/refspec. It only changes the default Push/Sync path to line up with what Git would do for git push.

I also verified the failure mode before the implementation: the new tests failed because VS Code pushed feature:main to the upstream remote. All tests fail for the right reasons, and pass after the changes.

[Copilot]

Pull request overview

This PR updates the built-in Git extension’s default Push and Sync behavior to stop constructing an explicit remote refspec from the upstream branch, and instead delegate push-target selection to Git’s own configuration (push.default, remote.pushDefault, triangular workflow), while keeping the pull/rebase side of Sync explicitly tied to the upstream branch.

Changes:

• Default Push and the push-half of Sync now run without an explicit remote/refspec so Git decides the destination.
• Sync UI messaging (confirmation + tooltip) no longer claims pushes go to the upstream branch.
• Adds Git integration tests covering push.default=current, remote.pushDefault, and “read-only upstream + configured push remote”.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
extensions/git/src/test/push.test.ts	Adds integration tests validating Push/Sync respect Git’s configured push destination (including read-only upstream scenarios).
extensions/git/src/repository.ts	Changes Push/Sync push execution to omit remote/refspec and updates Sync tooltip/label behavior accordingly.
extensions/git/src/commands.ts	Updates Sync confirmation prompt copy and removes upstream-remote read-only gating for prompting.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.