chore: enable and fixes rules from gocritic

.golangci.yml

@@ -3,6 +3,7 @@ version: "2"
 linters:
   enable:
     - errorlint
+    - gocritic
     - unconvert
     - unparam
   exclusions:
@@ -11,6 +12,18 @@ linters:
       - comments
       - std-error-handling
   settings:
+    gocritic:
+      disabled-checks:
+        - appendAssign
+        - builtinShadow
+        - deferInLoop
+        - hugeParam
+        - importShadow
+        - paramTypeCombine
+        - sloppyReassign
+        - unnamedResult
+        - whyNoLint
+      enable-all: true
     staticcheck:
       # Enable all options, with some exceptions.
       # For defaults, see https://golangci-lint.run/usage/linters/#staticcheck

capability/capability_linux.go

@@ -77,11 +77,12 @@ func mkString(c Capabilities, max CapType) (ret string) {
 	ret = "{"
 	for i := CapType(1); i <= max; i <<= 1 {
 		ret += " " + i.String() + "=\""
-		if c.Empty(i) {
+		switch {
+		case c.Empty(i):
 			ret += "empty"
-		} else if c.Full(i) {
+		case c.Full(i):
 			ret += "full"
-		} else {
+		default:
 			ret += c.StringCap(i)
 		}
 		ret += "\""

capability/capability_test.go

@@ -133,7 +133,7 @@ func TestNewPid2Load(t *testing.T) {
 	// Assuming that at least bounding set is not empty.
 	bset := c.StringCap(BOUNDING)
 	t.Logf("Bounding set: %s", bset)
-	if len(bset) == 0 {
+	if bset == "" {
 		t.Fatal("loaded bounding set: want non-empty, got empty")
 	}
 }

mount/sharedsubtree_linux_test.go

@@ -313,9 +313,7 @@ func TestSubtreeUnbindable(t *testing.T) {
 	} else if err == nil {
 		t.Fatalf("%q should not have been bindable", sourceDir)
 	}
-	defer func() {
-		if err := Unmount(targetDir); err != nil {
-			t.Fatal(err)
-		}
-	}()
+	if err := Unmount(targetDir); err != nil {
+		t.Fatal(err)
+	}
 }

user/idtools_unix.go

@@ -137,7 +137,7 @@ func lookupSubRangesFile(path string, usr User) ([]IDMap, error) {
 			ParentID: idrange.SubID,
 			Count:    idrange.Count,
 		})
-		containerID = containerID + idrange.Count
+		containerID += idrange.Count
 	}
 	return idMap, nil
 }