review: refuse a process named ".", ".." or with a leading dash, so removing one cannot delete the mesh's own directory (hq ADR 0118)

removeProcess deletes filepath.Join(daemonRoot, name) whole; a process named ".." made that
/var/lib/mesh. The declaration and the removal now hold the name to one rule.

internal/declaration/declaration.go

@@ -575,16 +575,34 @@ func (d *Process) Identity() string { return d.ID }
 func (d *Process) Kind() Type       { return TypeProcess }
 func (d *Process) Target() string   { return d.Name }
 
+// ProcessNameProblem says what is wrong with a process name, or nothing.
+//
+// The name becomes a unit name, a file under the unit directory and a directory under the mesh's
+// own — the one removing the process deletes, whole (novox/hq ADR 0118). So a name that is not one
+// plain path element is refused: with a separator it writes somewhere nobody meant, and "." or
+// ".." IS the mesh's directory or its parent — removing a process named ".." would delete every
+// bundle the mesh has, and more. One with a leading dash is read by the service manager as an
+// option, not a unit. Exported because the removal checks the recorded name again: a record is
+// what the host wrote, and a host of an older version wrote it under looser rules.
+func ProcessNameProblem(name string) string {
+	switch {
+	case name == "":
+		return "a process needs a name, which is what its unit is called"
+	case strings.ContainsAny(name, "/ \t"):
+		return "a process name becomes a unit name, so it cannot contain a path separator or a space"
+	case name == "." || name == "..":
+		return fmt.Sprintf("a process name becomes a directory under the mesh's own, and %q would be "+
+			"that directory or its parent", name)
+	case strings.HasPrefix(name, "-"):
+		return "a process name cannot begin with a dash: the service manager would read it as an option"
+	}
+	return ""
+}
+
 func (d *Process) validate(where string, _ bool) []string {
 	var problems []string
-	if d.Name == "" {
-		problems = append(problems, where+": a process needs a name, which is what its unit is called")
-	}
-	if strings.ContainsAny(d.Name, "/ \t") {
-		// It becomes a unit name and a file on disk. A name with a separator in it would write
-		// somewhere nobody meant.
-		problems = append(problems, where+": a process name becomes a unit name, so it cannot "+
-			"contain a path separator or a space")
+	if problem := ProcessNameProblem(d.Name); problem != "" {
+		problems = append(problems, where+": "+problem)
 	}
 	if d.Source == "" {
 		problems = append(problems, where+": a process needs somewhere to fetch its bundle from")

internal/declaration/process_test.go

@@ -55,7 +55,10 @@ func TestAProcessMustSayWhatToRun(t *testing.T) {
 
 // Its name becomes a unit name and a path, so a separator in it would write somewhere nobody meant.
 func TestAProcesssNameCannotEscapeItsUnit(t *testing.T) {
-	for _, bad := range []string{"", "../escape", "two words", "a/b"} {
+	// "." and ".." are one path element each, and the mesh's own bundle directory and its parent:
+	// removing a process named ".." would delete every bundle the mesh has, and more (novox/hq ADR
+	// 0118). A leading dash is an option to the service manager, not a unit.
+	for _, bad := range []string{"", "../escape", "two words", "a/b", ".", "..", "-", "--now"} {
 		d := aProcess()
 		d.Name = bad
 		if problems := d.validate("a process", false); len(problems) == 0 {