Enforce import order

.github/.golangci.yml

@@ -0,0 +1,14 @@
+linters:
+  disable-all: true
+  enable:
+    - gci
+linters-settings:
+  gci:
+    sections:
+      - standard
+      - default
+      - Prefix(github.com/canonical/pebble)
+issues:
+  # these values ensure that all issues will be surfaced
+  max-issues-per-linter: 0
+  max-same-issues: 0

.github/workflows/lint.yml

@@ -0,0 +1,30 @@
+name: Lint
+on: [push, pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/setup-go@v4
+        with:
+          go-mod-file: 'go.mod'
+          cache: false
+
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v3
+        id: lint
+        with:
+          version: latest
+          args: '-c .github/.golangci.yml --out-format=colored-line-number'
+          skip-cache: true
+
+      - name: Print error message
+        if: always() && steps.lint.outcome == 'failure'
+        run: |
+          echo '
+          Linting failed. On your local machine, please run
+              golangci-lint run -c .github/.golangci.yml --fix
+          and check in the changes.'
+          exit 1

HACKING.md

@@ -83,6 +83,39 @@ $ curl --unix-socket ~/pebble/.pebble.socket 'http://localhost/v1/services?names
 ```
 
 
+## Code style
+
+Pebble imports should be arranged in three groups:
+- standard library imports
+- third-party / non-Pebble imports
+- Pebble imports (i.e. those prefixed with `github.com/canonical/pebble`)
+
+Imports should be sorted alphabetically within each group.
+
+We use the [`gopkg.in/check.v1`](https://pkg.go.dev/gopkg.in/check.v1) package for testing. Inside a test file, import this as follows:
+```go
+. "gopkg.in/check.v1"
+```
+so that identifiers from that package will be added to the local namespace.
+
+
+Here is an example of correctly arranged imports:
+
+```go
+import (
+	"fmt"
+	"net"
+	"os"
+
+	"github.com/gorilla/mux"
+	. "gopkg.in/check.v1"
+
+	"github.com/canonical/pebble/internals/systemd"
+	"github.com/canonical/pebble/internals/testutil"
+)
+```
+
+
 ## Running the tests
 
 Pebble has a suite of Go unit tests, which you can run using the regular `go test` command. To test all packages in the Pebble repository:

internals/cli/cli.go

@@ -26,7 +26,6 @@ import (
 	"unicode/utf8"
 
 	"github.com/canonical/go-flags"
-
 	"golang.org/x/crypto/ssh/terminal"
 
 	"github.com/canonical/pebble/client"

internals/cli/cli_test.go

@@ -11,7 +11,6 @@ import (
 	"testing"
 
 	"golang.org/x/crypto/ssh/terminal"
-
 	. "gopkg.in/check.v1"
 
 	"github.com/canonical/pebble/cmd"

internals/cli/format_test.go

@@ -18,9 +18,6 @@ import (
 	"os"
 	"runtime"
 
-	// "fmt"
-	// "net/http"
-
 	"gopkg.in/check.v1"
 
 	"github.com/canonical/pebble/internals/cli"

internals/daemon/api_changes_test.go

@@ -23,9 +23,9 @@ import (
 	"net/http/httptest"
 	"time"
 
-	"github.com/canonical/pebble/internals/overlord/state"
-
 	"gopkg.in/check.v1"
+
+	"github.com/canonical/pebble/internals/overlord/state"
 )
 
 func setupChanges(st *state.State) []string {

internals/daemon/api_files_test.go

@@ -32,9 +32,10 @@ import (
 	"syscall"
 	"time"
 
+	. "gopkg.in/check.v1"
+
 	"github.com/canonical/pebble/internals/osutil"
 	"github.com/canonical/pebble/internals/osutil/sys"
-	. "gopkg.in/check.v1"
 )
 
 var _ = Suite(&filesSuite{})

internals/daemon/api_services_test.go

@@ -25,9 +25,9 @@ import (
 	"strings"
 	"time"
 
-	"github.com/canonical/pebble/internals/overlord/state"
-
 	. "gopkg.in/check.v1"
+
+	"github.com/canonical/pebble/internals/overlord/state"
 )
 
 var servicesLayer = `

internals/daemon/api_warnings_test.go

@@ -21,9 +21,9 @@ import (
 	"net/url"
 	"time"
 
-	"github.com/canonical/pebble/internals/overlord/state"
-
 	"gopkg.in/check.v1"
+
+	"github.com/canonical/pebble/internals/overlord/state"
 )
 
 func (s *apiSuite) testWarnings(c *check.C, all bool, body io.Reader) (calls string, result interface{}) {

internals/daemon/daemon.go

@@ -31,9 +31,8 @@ import (
 	"syscall"
 	"time"
 
-	"gopkg.in/tomb.v2"
-
 	"github.com/gorilla/mux"
+	"gopkg.in/tomb.v2"
 
 	"github.com/canonical/pebble/internals/logger"
 	"github.com/canonical/pebble/internals/osutil"