Fixing an edge case in lockdiff where all the projects may be removed…

… from the lock file.

gps/verify/lockdiff.go

@@ -95,6 +95,13 @@ func DiffLocks(l1, l2 gps.Lock) LockDelta {
 			Name: pr1,
 		}
 
+		// Edge case: If there are no lockedProjects on the RHS, they have most probably been removed from the lock file.
+		if len(p2) == 0 {
+			lpd.ProjectRemoved = true
+			diff.ProjectDeltas[pr1] = lpd
+			continue
+		}
+
 		for i2 := i2next; i2 < len(p2); i2++ {
 			lp2 := p2[i2]
 			pr2 := lp2.Ident().ProjectRoot

gps/verify/lockdiff_test.go

@@ -118,6 +118,10 @@ func TestLockDelta(t *testing.T) {
 			lt:    dup.addII("other.org").rmII("baz.com/qux").addDumbProject("zebrafun.org").rmProject("foo.com/bar"),
 			delta: InputImportsChanged | ProjectRemoved | ProjectAdded,
 		},
+		"remove all projects and imports": {
+			lt:    dup.rmII("baz.com/qux").rmII("foo.com/bar").rmProject("baz.com/qux").rmProject("foo.com/bar").rmProject("transitive.com/dependency"),
+			delta: InputImportsChanged | ProjectRemoved,
+		},
 	}
 
 	for name, fix := range tt {