Allow users to lazy load on another package

doc/dep.txt

@@ -15,6 +15,7 @@ Table of Contents                                      *dep-table-of-contents*
 6. Examples                                                     |dep-examples|
   - Declaring Dependencies               |dep-examples-declaring-dependencies|
   - Modules                                             |dep-examples-modules|
+  - Lazy Loading                                   |dep-examples-lazy-loading|
 7. Credits & License                                             |dep-credits|
 
 ==============================================================================
@@ -293,6 +294,27 @@ into the options table to re-run the binding after loading the package. You
 may choose to include your own logic by passing a function to the `rerun`
 field or disable the built-in logic by passing false.
 
+------------------------------------------------------------------------------
+LOAD:PLUGIN                                      *dep-lazy-loading-api-plugin*
+
+`load:plugin` is a function which allows you to specify another plugin for the
+package to load after. It takes two arguments: `plugin` which is the name of
+the plugin you want to follow like: 'user/package'. The second argument is
+`opts` which is a table with one option: `callback` which is a function. The
+following is an example:
+>lua
+  load:plugin("user/package", {})
+<
+Which is the same as:
+>lua
+  load:plugin("user/package", {
+    callback = function()
+      self:cleanup()
+    end
+  })
+<
+When 'user/package' is already loaded the `callback` is called immediately.
+
 LAZY LOADING API SHORTHANDS                  *dep-lazy-loading-api-shorthands*
 
 On occasion you may wish to only define one condition for the package to load.
@@ -589,6 +611,50 @@ declared in that module.
     }
   }
 <
+LAZY LOADING                                       *dep-examples-lazy-loading*
+
+Lazy loading is a very complicated topic, and therefore this part of the
+documentation assumes you have experience with regular package managment.
+Let's go over loading order, and how the lazy loader determines what needs to
+be loaded.
+
+Let's say we have the following spec:
+>lua
+  { "user/package",
+    lazy = true,
+    deps = "user/dependent"
+  }
+<
+This is the same as the following:
+>lua
+  { "user/package",
+    lazy = true
+  },
+
+  { "user/dependent",
+    reqs = "user/package",
+    lazy = require("dep.lazy.loader.short").plugin("user/package")
+  }
+<
+What you're seeing is implicit lazy loading. By default dep will lazy load
+dependents who are explicitly defined in the spec. Now if we we're to modify
+'user/dependent' like so:
+>lua
+  { "user/package",
+    lazy = true
+  },
+
+  { "user/dependent",
+    reqs = "user/package",
+    lazy = function(load)
+      load:plugin("user/package")
+      load:cmd("LoadDependent")
+    end
+  }
+<
+If we were to call the command `:LoadDependent` it would first load
+'user/package', and then load 'user/dependent'.
+
 ==============================================================================
 7. Credits & License                                             *dep-credits*