cli/compose/loader: mergeServices: remove intermediate map for overrides

The code was using an intermediate map, indexed by name, for services
per file. Service-names should be unique per-file, so using an intermediate
map would not benefit us (we'd still have to loop over all of them to
produce the map, and again to iterate over the map)

Remove the intermediate map for overrides, and apply all overrides for
a service instead.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

cli/compose/loader/merge.go

@@ -71,15 +71,15 @@ func mergeServices(base, override []types.ServiceConfig) ([]types.ServiceConfig,
 	}
 
 	baseServices := mapByName(base)
-	for name, overrideService := range mapByName(override) {
-		if baseService, ok := baseServices[name]; ok {
+	for _, overrideService := range override {
+		if baseService, ok := baseServices[overrideService.Name]; ok {
 			if err := mergo.Merge(&baseService, &overrideService, mergeOpts...); err != nil {
-				return base, fmt.Errorf("cannot merge service %s: %w", name, err)
+				return base, fmt.Errorf("cannot merge service %s: %w", overrideService.Name, err)
 			}
-			baseServices[name] = baseService
+			baseServices[overrideService.Name] = baseService
 			continue
 		}
-		baseServices[name] = overrideService
+		baseServices[overrideService.Name] = overrideService
 	}
 
 	services := make([]types.ServiceConfig, 0, len(baseServices))