Git panel: no way to list files changed on a branch since its base

Reproduction steps 1. Open a git repo in Zed and check out a branch other than the default branch. 2. Edit a few files and commit them. 3. Open the git panel. Current vs. Expected behavior Current behavior: the Changes tab lists only uncommitted files, so committed files disappear from it. git: diff branch shows the branch's changes, but as one multibuffer with no file list. There's no way to see or navigate the files a branch changed since its base (e.g. origin/main). Expected behavior: the git panel can list every file the branch changed since its base, including committed ones, so you can review the branch file by file. Zed version and system specs Zed: v1.26.2+stable.384.c4273271092b0287f7d181f616bd5171e0a2f70c (Zed) OS: macOS 27.0.1 Memory: 64 GiB Architecture: aarch64 Attach Zed log file _No response_ Relevant Zed settings _No response_ Relevant Keymap _No response_ (for AI issues) Model provider details _No response_ If you are using WSL on Windows, wh…