sync: implement reprojectcmd for the local half

2026-09-15T19:53:01+00:00

Add `repo.reprojectcmd`, the checkout counterpart to `repo.fetchcmd`. When set, `repo sync` runs this command instead of Git to materialize a project's index and worktree at the target tree, while `repo` handles ref updates directly via `git update-ref`. This replaces Git's tree materialization steps: detaching HEAD, fast-forwarding, and hard-resetting. Rebasing is not delegated, and the command is skipped if HEAD is already at the target, if HEAD is ahead of the target during fast-forward, or for MetaProjects. The command runs in a subshell with project environment variables (such as `REPO_TREV`). Before running, `repo` ensures no operation is in progress and no staged changes exist. Worktree collision detection is delegated to the command (preserving benign unstaged/untracked edits). Afterward, `repo` verifies that HEAD was untouched and that the index matches the target tree. Like `repo.fetchcmd`, this requires `repo.uselocalgitdirs`. Nested projects and submodules are unsupported; `repo sync` fails if the manifest contains any while `repo.reprojectcmd` is enabled. Verified end-to-end with repo init using local-gitdirs, repo.fetchcmd, and repo.reprojectcmd ('git -C $REPO_PATH read-tree -m -u $REPO_TREV'): * Verified detached HEAD checkout and correct reflog generation across projects. * Verified benign unstaged edits and untracked files survive checkout. * Verified conflicting untracked files fail with exit 128 without clobbering worktree. * Verified staged changes fail upfront before reprojectcmd is executed. Bug: 513329573 Change-Id: I964d24d22dccffc05a9b991ad69f3a7e93268c01 Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/626281 Tested-by: Gavin Mak Reviewed-by: Brian Gan Commit-Queue: Gavin Mak

tools/git-repo.git/docs/reproject-cmd.md, branch v2.72

sync: implement reprojectcmd for the local half