[WIP] Add change address to SendCoinsRequest (#10271)

CHANGE-10271.md

@@ -0,0 +1,31 @@
+# LND #10271 Implementation Guide
+
+## Changes Needed
+
+### 1. lnrpc/lightning.proto
+Add to `SendCoinsRequest`:
+```protobuf
+string change_address = 15;
+```
+
+### 2. cmd/lncli/commands.go
+Add flag:
+```go
+cli.StringFlag{
+    Name:  "change_address",
+    Usage: "Optional address to send change to",
+},
+```
+
+### 3. lnd/lnwallet/btcwallet/btcwallet.go
+Update `SendCoins` to use change address.
+
+## Generate Protobuf
+```bash
+make rpc
+```
+
+## Test
+```bash
+make check
+```

PR_TODO.md

@@ -0,0 +1,69 @@
+# PR #10769 Completion Checklist
+
+## Completed ✅
+- [x] Add `change_addr` field to `SendCoinsRequest` proto
+- [x] Add `--change_addr` flag to `sendcoins` CLI command
+- [x] Pass change address to SendCoins RPC call
+- [x] Push branch to fork
+- [x] Create upstream PR
+
+## Remaining Work 📝
+
+### 1. Regenerate Protobuf Code
+```bash
+make rpc
+```
+This will regenerate:
+- `lnrpc/lightning.pb.go`
+- `lnrpc/lightning_grpc.pb.go`
+
+### 2. Add Unit Tests
+Create `cmd/commands/commands_test.go` or update existing tests:
+```go
+func TestSendCoinsWithChangeAddr(t *testing.T) {
+    // Test that change_addr is properly parsed and passed
+}
+```
+
+### 3. Add Integration Tests
+Update `lntest/itest/lnd_on_chain_test.go`:
+```go
+func testSendCoinsWithChangeAddr(t *harnessTest) {
+    // Test sending coins with custom change address
+}
+```
+
+### 4. Update Documentation
+- Update `docs/cmd/lncli.md` if it exists
+- Add example usage to PR description
+
+### 5. Wallet Implementation
+The wallet needs to actually use the change address. Update:
+- `lnwallet/btcwallet/btcwallet.go` - `SendCoins` method
+- `rpcserver.go` - Pass change address to wallet
+
+## How to Get Write Access
+
+1. **Become a regular contributor:**
+   - Submit quality PRs
+   - Review other PRs
+   - Participate in discussions
+
+2. **Join the LND community:**
+   - Discord: https://discord.gg/lightning
+   - IRC: #lnd on Libera.Chat
+   - Mailing list: lightning-dev
+
+3. **Build reputation:**
+   - Fix bugs
+   - Add features
+   - Write documentation
+
+4. **Apply for maintainership:**
+   - After consistent contributions
+   - Ask existing maintainers
+
+## Current Status
+- PR is open and ready for review
+- Basic implementation is complete
+- Needs protobuf regeneration and tests

cmd/commands/commands.go

@@ -536,6 +536,12 @@ var sendCoinsCommand = cli.Command{
 				"the amt flag",
 		},
 		txLabelFlag,
+		cli.StringFlag{
+			Name: "change_addr",
+			Usage: "(optional) an address to send the change to; if " +
+				"unset, the change will be returned to the wallet's " +
+				"change output",
+		},
 	},
 	Action: actionDecorator(sendCoins),
 }
@@ -682,6 +688,7 @@ func sendCoins(ctx *cli.Context) error {
 		SpendUnconfirmed:      minConfs == 0,
 		CoinSelectionStrategy: coinSelectionStrategy,
 		Outpoints:             outpoints,
+		ChangeAddr:            ctx.String("change_addr"),
 	}
 	txid, err := client.SendCoins(ctxc, req)
 	if err != nil {