Supply line

In Fallout 4, Supply lines can be created between settlements to share resources and inventory among them.

Requirements for creating supply lines:
 * At least 2 owned settlements
 * 1 free settler
 * At least Level 1 in the Local Leader perk

Benefits
Linking your settlements with supply lines provides the following benefits:
 * When building at a workshop or using a crafting station inside a settlement, you can use the inventory of all linked workshops/crafting stations (though the shared items will not all show up in the workspace, they will automatically be used when crafting/building).
 * Even non-junk items will be shared, so long as they are in your workspace (such as mods or items like Purified Water); they will automatically be used when a recipe calls for it.
 * Excess food/water will be used to supply the settlements in the supply network with shortages; this is only indicated by the normal "red" display for food/water shortages being green. Moreover, it may not turn green immediately; doing something to force the UI to update, such as assigning another settler to a defense job may correct this.
 * In your PIP Boy "Workshop" menu, the game may still show a food/water shortage in settlements that have less food or water than their population, but so long as you have supply lines established, all that matters is the total population compared to the total food and water production you have within your connected supply network.

Usage
To create a supply line, use the workshop in one of your settlements, highlight a settler and press [Q] (or R1/RB on PS4/XBOX) to display a list of owned settlements. Select the settlement you want to link to your current settlement to.

To review existing supply lines, open the world map and press [C] (or L1/LB on PS4/XBOX) to view all the settlements connected to the Supply Line network.

Settlers assigned to supply lines will become Provisioners and will travel between settlements (usually leading a pack-brahmin). If you ever want to remove the supply line, simply reassign the Provisioner to some other work object in their settlement.


 * The Provisioner will actually travel between the two connected settlements, so it may be difficult to reassign the worker, since they may not be in their home settlement.
 * Provisoners still count towards the population limit of their respective settlements, as well as food/water requirements, despite hardly ever being in the settlement.
 * Settlements share resources with all other settlements that are part of its supply line network. Two settlements do not have to be directly connected. In other words, if you connect settlement A->B, B->C, and B->D, then A, C, and D will also share resources with each other despite not directly being connected since they are still part of the same network.
 * Provisioners will engage hostile creatures and enemies along their path, so it is advisable to equip them with appropriate weapons and armor so they can defend themselves.
 * Provisioners cannot die. Like companions, when taken enough damage, provisioners will be briefly knocked down, but they will get back up after a while.
 * Creating a supply network with two overlapping circles (A->B->C->D->A and A->C) can make some of the settlements have their food/water set to 0. To fix this you need to remove one of the circles and then activate the workshop at the affected settlements to update their resources.