fix: make git merge2 work across worktrees

Checkout of the target branch fails when it is already used by another worktree. Detect that worktree and merge there instead.
2026-09-10 23:04:13 +08:00
parent a834c46b89
commit 097fce7827
2 changed files with 74 additions and 1 deletions
@@ -0,0 +1,72 @@
+#!/bin/bash
+# 把当前分支 merge 进目标分支；目标已在其它 worktree 时直接在那边 merge
+set -euo pipefail
+
+usage() {
+    cat <<'EOF'
+用法: git merge2 <branch> [git merge 参数...]
+
+把当前分支合进 <branch>，然后留在当前分支。
+
+若 <branch> 已在其它 worktree 里 checkout，则在那个 worktree 里 merge，
+不会在当前目录 checkout（避免 "already used by worktree"）。
+EOF
+}
+
+if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
+    usage
+    exit 0
+fi
+
+if [[ $# -lt 1 ]]; then
+    usage >&2
+    exit 1
+fi
+
+current="$(git symbolic-ref --short HEAD)"
+target="$1"
+shift
+
+if [[ "$current" == "$target" ]]; then
+    echo "已经在 $target 上" >&2
+    exit 1
+fi
+
+# porcelain 含主 worktree；%(worktreepath) 只填 linked worktree，不能用
+worktree_for_branch() {
+    local branch="$1"
+    local wt=""
+    local line
+    while IFS= read -r line || [[ -n "$line" ]]; do
+        case "$line" in
+            worktree\ *)
+                wt="${line#worktree }"
+                ;;
+            "branch refs/heads/${branch}")
+                printf '%s\n' "$wt"
+                return 0
+                ;;
+            "")
+                wt=""
+                ;;
+        esac
+    done < <(git worktree list --porcelain)
+    return 1
+}
+
+# alias / 子进程会继承当前 worktree 的 GIT_DIR，必须清掉才能 git -C 到另一个 worktree
+merge_in_worktree() {
+    local wt="$1"
+    shift
+    env -u GIT_DIR -u GIT_WORK_TREE git -C "$wt" merge "$@"
+}
+
+wt="$(worktree_for_branch "$target" || true)"
+if [[ -n "$wt" ]]; then
+    echo "在 worktree 中 merge $current -> $target: $wt"
+    merge_in_worktree "$wt" "$current" "$@"
+else
+    git checkout "$target"
+    git merge "$current" "$@"
+    git checkout "$current"
+fi