cli/dot: Add edge tooltips

Here I add a tooltip for the graph edges, this will indicate the two
nodes that this edge connects and the kind of dependency that it is
representing.  This should be beneficial when looking at rather
complicated graphs.

Author: IdlePhysicist

internal/cli/dot.go

@@ -170,6 +170,25 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 			panic(err)
 		}
 
+		// Helper function to add an edge with a tooltip describing both nodes and dependency type
+		addEdgeWithTooltip := func(from, to *dot.Node, fromName, toName, depType string) error {
+			edge := dot.NewEdge(from, to)
+
+			if web {
+				tooltip := fmt.Sprintf("%s → %s", fromName, toName)
+				if depType != "" {
+					tooltip += fmt.Sprintf(" (%s)", depType)
+				}
+
+				if err := edge.Set("tooltip", tooltip); err != nil {
+					return err
+				}
+			}
+
+			_, err := out.AddEdge(edge)
+			return err
+		}
+
 		file := dot.NewNode(configFile)
 		if _, err := out.AddNode(file); err != nil {
 			panic(err)
@@ -187,7 +206,7 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 				}
 			}
 
-			if _, err := out.AddEdge(dot.NewEdge(file, n)); err != nil {
+			if err := addEdgeWithTooltip(file, n, configFile, pkg, "required"); err != nil {
 				panic(err)
 			}
 			if before, _, ok := strings.Cut(pkg, "="); ok {
@@ -201,7 +220,7 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 						panic(err)
 					}
 				}
-				if _, err := out.AddEdge(dot.NewEdge(n, p)); err != nil {
+				if err := addEdgeWithTooltip(n, p, pkg, before, "exact version"); err != nil {
 					panic(err)
 				}
 
@@ -233,7 +252,7 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 						panic(err)
 					}
 				}
-				if _, err := out.AddEdge(dot.NewEdge(n, p)); err != nil {
+				if err := addEdgeWithTooltip(n, p, pkg, before, "compatible version"); err != nil {
 					panic(err)
 				}
 
@@ -329,7 +348,7 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 				if _, ok := edges[dep]; !ok || !span {
 					// This check is stupid but otherwise cycles render dumb.
 					if pkg.Name != dep {
-						if _, err := out.AddEdge(dot.NewEdge(n, d)); err != nil {
+						if err := addEdgeWithTooltip(n, d, pkg.Name, dep, "dependency"); err != nil {
 							panic(err)
 						}
 						edges[dep] = struct{}{}
@@ -396,7 +415,7 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 								panic(err)
 							}
 
-							if _, err := out.AddEdge(dot.NewEdge(p, n)); err != nil {
+							if err := addEdgeWithTooltip(p, n, before, pkg.Name, "provides"); err != nil {
 								panic(err)
 							}
 						}
@@ -417,7 +436,7 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 								panic(err)
 							}
 
-							if _, err := out.AddEdge(dot.NewEdge(p, n)); err != nil {
+							if err := addEdgeWithTooltip(p, n, before, pkg.Name, "provides"); err != nil {
 								panic(err)
 							}
 						}
@@ -437,7 +456,7 @@ func DotCmd(ctx context.Context, configFile string, archs []types.Architecture,
 					}
 				}
 				if _, ok := edges[pkg.Name]; !ok || !span {
-					if _, err := out.AddEdge(dot.NewEdge(p, n)); err != nil {
+					if err := addEdgeWithTooltip(p, n, prov, pkg.Name, "provides"); err != nil {
 						panic(err)
 					}
 					edges[pkg.Name] = struct{}{}