feat: respect GIT_DIR and GIT_WORK_TREE environment variables

packages/opencode/src/project/project.ts

@@ -48,6 +48,93 @@ export namespace Project {
     log.info("fromDirectory", { directory })
 
     const { id, sandbox, worktree, vcs } = await iife(async () => {
+      const envGitDir = process.env.GIT_DIR
+      const envWorkTree = process.env.GIT_WORK_TREE
+
+      if (envGitDir && (await fs.stat(envGitDir).catch(() => undefined))) {
+        log.info("using GIT_DIR from environment", { envGitDir, envWorkTree })
+        const gitBinary = Bun.which("git")
+        if (!gitBinary) {
+          return {
+            id: "global",
+            worktree: envWorkTree ?? directory,
+            sandbox: envWorkTree ?? directory,
+            vcs: Info.shape.vcs.parse(Flag.OPENCODE_FAKE_VCS),
+          }
+        }
+
+        const git = envGitDir
+        let sandbox = envWorkTree ?? directory
+
+        let id = await Bun.file(path.join(git, "opencode"))
+          .text()
+          .then((x) => x.trim())
+          .catch(() => undefined)
+
+        if (!id) {
+          const roots = await $`git rev-list --max-parents=0 --all`
+            .env({ ...process.env, GIT_DIR: git })
+            .quiet()
+            .nothrow()
+            .text()
+            .then((x) =>
+              x
+                .split("\n")
+                .filter(Boolean)
+                .map((x) => x.trim())
+                .toSorted(),
+            )
+            .catch(() => undefined)
+
+          id = roots?.[0]
+          if (id) {
+            void Bun.file(path.join(git, "opencode"))
+              .write(id)
+              .catch(() => undefined)
+          }
+        }
+
+        if (!id) {
+          return {
+            id: "global",
+            worktree: sandbox,
+            sandbox,
+            vcs: "git",
+          }
+        }
+
+        if (!envWorkTree) {
+          const top = await $`git rev-parse --show-toplevel`
+            .env({ ...process.env, GIT_DIR: git })
+            .quiet()
+            .nothrow()
+            .text()
+            .then((x) => x.trim())
+            .catch(() => undefined)
+
+          if (top) sandbox = top
+        }
+
+        const worktree = await $`git rev-parse --git-common-dir`
+          .env({ ...process.env, GIT_DIR: git })
+          .quiet()
+          .nothrow()
+          .text()
+          .then((x) => {
+            const dirname = path.dirname(x.trim())
+            if (dirname === ".") return sandbox
+            return dirname
+          })
+          .catch(() => sandbox)
+
+        return {
+          id,
+          sandbox,
+          worktree,
+          vcs: "git",
+        }
+      }
+
       const matches = Filesystem.up({ targets: [".git"], start: directory })
       const git = await matches.next().then((x) => x.value)
       await matches.return()

packages/opencode/test/project/project.test.ts

@@ -89,6 +89,84 @@ describe("Project.fromDirectory with worktrees", () => {
   })
 })
 
+describe("Project.fromDirectory with GIT_DIR/GIT_WORK_TREE env vars", () => {
+  test("should respect GIT_DIR and GIT_WORK_TREE when both are set", async () => {
+    await using tmp = await tmpdir({ git: true })
+
+    // Create a separate directory that is NOT a git repo
+    const separateDir = path.join(tmp.path, "..", "separate-dir")
+    await $`mkdir -p ${separateDir}`.quiet()
+
+    // Set env vars to point to the git repo
+    const originalGitDir = process.env.GIT_DIR
+    const originalWorkTree = process.env.GIT_WORK_TREE
+    try {
+      process.env.GIT_DIR = path.join(tmp.path, ".git")
+      process.env.GIT_WORK_TREE = tmp.path
+
+      // Call fromDirectory with the separate (non-git) directory
+      const { project } = await Project.fromDirectory(separateDir)
+
+      // Should detect the git repo from env vars, not filesystem walk
+      expect(project.vcs).toBe("git")
+      expect(project.worktree).toBe(tmp.path)
+    } finally {
+      if (originalGitDir === undefined) delete process.env.GIT_DIR
+      else process.env.GIT_DIR = originalGitDir
+      if (originalWorkTree === undefined) delete process.env.GIT_WORK_TREE
+      else process.env.GIT_WORK_TREE = originalWorkTree
+      await $`rm -rf ${separateDir}`.quiet().nothrow()
+    }
+  })
+
+  test("should respect only GIT_DIR and derive worktree", async () => {
+    await using tmp = await tmpdir({ git: true })
+
+    const separateDir = path.join(tmp.path, "..", "separate-dir-2")
+    await $`mkdir -p ${separateDir}`.quiet()
+
+    const originalGitDir = process.env.GIT_DIR
+    const originalWorkTree = process.env.GIT_WORK_TREE
+    try {
+      process.env.GIT_DIR = path.join(tmp.path, ".git")
+      delete process.env.GIT_WORK_TREE
+
+      const { project } = await Project.fromDirectory(separateDir)
+
+      expect(project.vcs).toBe("git")
+      expect(project.worktree).toBe(tmp.path)
+    } finally {
+      if (originalGitDir === undefined) delete process.env.GIT_DIR
+      else process.env.GIT_DIR = originalGitDir
+      if (originalWorkTree === undefined) delete process.env.GIT_WORK_TREE
+      else process.env.GIT_WORK_TREE = originalWorkTree
+      await $`rm -rf ${separateDir}`.quiet().nothrow()
+    }
+  })
+
+  test("should fall back to filesystem walk when GIT_DIR is invalid", async () => {
+    await using tmp = await tmpdir({ git: true })
+
+    const originalGitDir = process.env.GIT_DIR
+    const originalWorkTree = process.env.GIT_WORK_TREE
+    try {
+      process.env.GIT_DIR = "/nonexistent/path/.git"
+      process.env.GIT_WORK_TREE = "/nonexistent/path"
+
+      // Should fall back to filesystem walk and find the actual git repo
+      const { project } = await Project.fromDirectory(tmp.path)
+
+      expect(project.vcs).toBe("git")
+      expect(project.worktree).toBe(tmp.path)
+    } finally {
+      if (originalGitDir === undefined) delete process.env.GIT_DIR
+      else process.env.GIT_DIR = originalGitDir
+      if (originalWorkTree === undefined) delete process.env.GIT_WORK_TREE
+      else process.env.GIT_WORK_TREE = originalWorkTree
+    }
+  })
+})
+
 describe("Project.discover", () => {
   test("should discover favicon.png in root", async () => {
     await using tmp = await tmpdir({ git: true })