dev-doctor: add check for the root directory

Currently Cilium's build infrastructure assumes that Cilium is checked
out in ${GOPATH}/src/github.com/cilium/cilium, and will fail in
unpredictable ways if it is not.

This PR adds a check to the dev-doctor target to alert developers when
this is the case.

Signed-off-by: Tom Payne <tom@isovalent.com>

tools/dev-doctor/rootcmd.go

@@ -1,4 +1,4 @@
-// Copyright 2020 Authors of Cilium
+// Copyright 2020-2021 Authors of Cilium
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -50,6 +50,9 @@ func rootCmdRun(cmd *cobra.Command, args []string) {
 	checks := []check{
 		osArchCheck{},
 		unameCheck{},
+		rootDirCheck{
+			rootDir: "$GOPATH/src/github.com/cilium/cilium",
+		},
 		&binaryCheck{
 			name:          "make",
 			ifNotFound:    checkError,

tools/dev-doctor/rootdircheck.go

@@ -0,0 +1,77 @@
+// Copyright 2021 Authors of Cilium
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+	"strings"
+)
+
+// A rootDirCheck checks that Cilium is checked out in path. Environment
+// variables in path are expanded with os.ExpandEnv.
+type rootDirCheck struct {
+	rootDir string
+}
+
+func (c rootDirCheck) Name() string {
+	return "root-dir"
+}
+
+func (c rootDirCheck) Run() (checkResult, string) {
+	goPath := os.Getenv("GOPATH")
+	if goPath == "" {
+		return checkWarning, "$GOPATH is not set"
+	}
+
+	dir, err := os.Getwd()
+	if err != nil {
+		return checkError, fmt.Sprintf("cannot get working directory: %s", err)
+	}
+
+	// Search upward through through parent directories to find the .git directory.
+	for {
+		info, err := os.Stat(path.Join(dir, ".git"))
+		switch {
+		case err == nil && info.Mode().IsDir():
+			if dir != os.ExpandEnv(c.rootDir) {
+				foundDir := dir
+				if strings.HasPrefix(dir, goPath+"/") {
+					foundDir = "$GOPATH/" + dir[len(goPath)+1:]
+				}
+				return checkWarning, fmt.Sprintf("found %s, want %s", foundDir, c.rootDir)
+			}
+			return checkOK, fmt.Sprintf("found %s", c.rootDir)
+		case err == nil:
+			// .git exists in dir but is not a directory, continue searching upward.
+		case errors.Is(err, fs.ErrNotExist):
+			// .git does not exist in dir, continue searching upward.
+		default:
+			return checkError, fmt.Sprintf("stat %s: %v", dir, err)
+		}
+
+		if dir == "/" {
+			return checkError, "could not find root directory"
+		}
+		dir = path.Dir(dir)
+	}
+}
+
+func (c rootDirCheck) Hint() string {
+	return fmt.Sprintf("run git clone https://github.com/cilium/cilium.git %s && cd %s", c.rootDir, c.rootDir)
+}